On the top three games for memorable characters and canon.

[Der_Bright_Poster]

I have just went through a mental checklist on some of the games and I have got to say Touhou has got some memorable characters however, I also noted that some games have just had a lasting effect even after a dozen or so games. This is my personal top 3 I would also like to see yours as well.  Please pick games just from the main series. Also you don't have to justify your choices in the series as much as I have. It is just my personal preference that I do.

1. Embodiment of Scarlet Devil, this game is perhaps the biggest because of one certain character that we know throughout the fanbase the nine ball ⑨, Cirno. She would go on to create team ⑨. More than two games after her, appeared in the  spin-off game Hisoutensoku when she then got a entire game Fairy Wars when she was given a break from the spotlight afterwards. She is indeed one of the strongest characters. Also ESoD we got the Scarlet sisters. Both of whom are remember in the fanbase. Remilia Scarlet has appeared in every fighting game until Touhou Hisoutensoku and was featured in Imperishable Night. Sakuya is also a fan favorite who has appeared in a few of the main shmups  games along with all of the  all of the fighting games until Hisoutensoku.

2. Perfect Cherry Blossom, this game established our current understanding of the Touhou verse, while also having rememberable characters. Alice has appeared in every fighting game until Hisoutensoku. She has memorable often being placed very close with the main character Marisa and she maybe a survivor of the lose PC-98 era of characters. The Netherworld world character, the couple has appeared in every fighting game up until Hisoutensoku (of course.) youmu has even been featured as a main character in a couple of the main series and Yuyuko has appeared in a game within the main series as well as a playable character. We also get the Yakumo clan who play a very prominent role in canon. We also get the fan favorite band from this game the Prismriver sisters.

3. Finally Mountain of Faith. This game in the series for me showcases the series attempt as whole to get out from the under the shadows of the previous games to establish new characters and new factions that aren't overshadowed by previous games prominence. We got Nitori a new character that might be just as prominent as the alice character in the series in terms of shipping with Marisa. We get Sanae who has been featured in 3 of the main games as a playable character since her reveal and the game has had a major affects in canon that has brought us the characters from Subterranean Animism as well as Unidentifiable Fantastical Object. Also after this game in the series games began to feature multiple scenarios based upon your shot type. Those are my top three games in the series.

[Boomer]

My personal list will be made based more on which games left the biggest impression on me.

1. Embodiment of Scarlet Devil: I don't think that there is any character in this game that I dislike, I enjoyed their boss fights as well as reading their dialogue.  This is also the first main series game that I have played outside of the PC-98 games.  Finally, it debuted my favourite character, Sakuya Izayoi.

2. Imperishable Night: This is probably one of my favourites in the main series in terms of gameplay mechanics and characters.  I personally really liked the idea of the human/phantom side mechanic for I found that it added some tactical potential and just added some more liveliness to the game, especially during pre-battle dialogue.

3. Phantasmagoria of Dim Dream: I don't really play this one much anymore, but it did leave a big impression due to its more VS. styled gameplay.  The PC-98 games were the first Touhou games I ever played and this was probably the most addicting one of them all.  I also found that it as well as Flower View required a much larger skill set for it was not as predictable as the other main series games.

Honourable mentions: Perfect Cherry Blossom, Mountain of Faith.

[Ryuunotaki]

For me, my list would be like this:

3. Ten Desires
I have been a fan of the series for a long while, but before TD, I barely played the shooters at all-- it was usually the fighters I played. When people started saying how TD is supposedly easier than the other shooters, I tried it out and I ended up enjoying the act of dodging danmaku. TD makes it to my list since it is what made me appreciate Touhou's shooters.

2. Perfect Cherry Blossom
This was the first shooter I ever played and while I didn't dig danmaku until the arrival of TD, this game, with its wonderful music and beautiful patterns, really left a big impact on me. Its music evokes a sense of nostalgia in me, now. I listen to PCB's songs (arranged or not) and I remember those high school days of mine...
ah.
I want to drink some Premium Sapporo.

1. Legacy of Lunatic Kingdom
Yes, I know it's new, but that isn't why it's number one.
Where PCB anchored me to Touhou with its music and where TD taught me to appreciate Danmaku, LoLK not only greatly matured my obsession of and appreciation for Danmaku, but also gave me severe chills with just how beautifully done the backgrounds and the music were! And there's LoLK's highly complex storyline.

That's it for most memorable--- their characters are memorable because their games are. For most significant to canon, we have:

3. Lotus Land Story
LLS was where Reimu was introduced to her best friend and rival, Marisa-- who is to later serve a big role in canon. If this isn't significant, I don't know what is.

2. Mountain of Faith
Starting with MoF, the games started getting entwined with each other through their storyline, going beyond being just a set of independent games sharing the same setting and started becoming a real series. MoF caused the first chain reaction in Touhou. That's pretty significant.

1. Legacy of Lunatic Kingdom
LoLK has the most complex yet, and potentially with very far-reaching consequences. The Lunar Capital was being invaded by fairies and thus sullied by the presence of life and death--- where do they go? It's not like they can live in the dream world forever... right? What is a Greek doing in Touhou?
LoLK also opened (or at least widened the opening of the lid on) a can of worms by introducing overpowered characters (either present or mentioned) that (at least in LoLK) are not unwilling to kill. (such as whoever sent that drone into Gensokyo)
LoLK can be the start of a new era.

edit: added 'significant to canon' entries

[Schneeless]

Very interesting topic. I've thought a while about this. And I'd have to say...

3. Highly Responsive to Prayers- I realllly wasn't sure whether to put this at number 2 or 3, but due to the lack of memorable characters(aside from Mima), the only thing it has going for it is that it's the first Touhou game. It's what started all of this. If this game was never made, then Touhou probably would've never existed. Although it may not have many memorable characters or contributes much to canon, this is where Reimu's journey started. This is where Touhou started.

2. Perfect Cherry Blossom- PCB has tons of memorable characters and contributed a lot to the world and story of Touhou. Alice is a well-known and loved character by fans, provides material for fan works with Marisa and others, and appeared in the PC-98 games and some fighting games. The Netherworld is very interesting and provides a lot for the Touhou world. Yuyuko and Youmu are very well known and loved across the community. Though what really gets PCB all the way to number 2 is the Yakumo family, specifically Yukari. Yukari is one of the most influential characters in both canon and fan works. She provides a basis on how and why Gensokyo was made. She has been involved in many of the past events in Gensokyo and she is one of the strongest if not the strongest youkai in it. She is very well-known in the Touhou community, and will continue to be so for a very long time.

1. Embodiment of Scarlet Devil- And now, for number 1. EoSD is in my opinion the game with the most memorable characters that have stayed well-known and loved for all these years. Let's start with Cirno, she is very well known, partly due to the ⑨. She has her own game where she is the main character, the ⑨ team, and has appeared in many other games as a stage 1 mid boss or as a fighting game character. Meiling and Patchouli are pretty well known and have appeared in several other fighting games. Now, a character who used to be my favorite(and still is one of mine), is Sakuya, who has appeared as a playable character many times alongside Reimu and Marisa. She is well-loved and known by the community.  Lastly, the Scarlet sisters are still loved by the community even after all these years. Heck, Flandre appeared in only one game, and she is one of the most popular characters in all of Touhou. EoSD is the first Windows Touhou game and paved the way for the rest to come.

Honorable Mentions:MoF, UFO, IN, and SA.

[TresserT]

I'd just like to say, these are by no means my favorite games to play, just the games I think helped touhou along the most.

1) Imperishable Night
This was what EoSD and PCB were leading up to; this is what ZUN had been planning since the start of the windows series. While it didn't introduce many new characters, it took a ton of the old ones and expanded on their stories and personalities. Without this game, Remilia would be a Dracula clone instead of a strange little girl. Yuyuko would just be a suicide ghost girl instead of the eccentric-yet-wise food lover we know. We wouldn't have Mari/Ali interactions. Nothing like this would come in a main game until SA, and even then it wasn't done as comprehensively.

2) Embodiment of Scarlet Devil.
In PC-98, ZUN hadn't developed a real canon yet. EoSD was the first time ZUN began to world build instead of just throw in random enemies. In other words, EoSD is where ZUN really began to think about Gensokyo. In addition,it brought us the fan favorites of Cirno, Meiling, Patchouli, Sakuya, Remilia, and Flandre (sorry Rumia =P). However, while it brought a lot to the table, a lot was also swept away in PCB and IN. Most of EoSD's story was retconned in later games, and EoSD's characters didn't really get any personality until IaMP, IN, PoFV, and Hisoutensoku.

3) Mountain of Faith.
This may not be the game that started it all, but it's the game that defines touhou as it is today. Besides the danmaku being less spammy, Mountain of Faith refines ZUN's world building, turning it into a series rather than a cluster of standalone games. After MoF, each game (more or less) connects directly into the next one. However, Mountain of Faith can't really take all the credit like IN or EoSD. It was tthe first link in the chain, but you can't make a chain with only one link.