But most of those games were released over 15 years ago.
Yeah, and MK 9, which pretty much reboot the series, and included just about every MK character worth mentioning, only had 7 more characters than this. It was the 9th game in the series, and it didn't even add a single new character to the game/series (save for DLC).
And vanilla Street Fighter IV had LESS playable characters than this game does.
And let's be honest here, how many of them are shoto clones? Ryu, Ken, Akuma, Gouken, Sakura, Dan, Sagat... MK doesn't fare much better, either. And SSB has clones of clones.
If people want to compare roster sizes, compare it to actual rosters, and in context. Yes, some games have huge rosters compared to this game. Some games have done amazing things (like, I don't know, completely jump-started the fighting game resurgence?) with a smaller roster.
Roster SIZE has little to do with anything. Roster STRENGTH is important. And this game, to me, has a very strong roster, who is quite varied.