Of course they do, but there are less fans. I also suppose it plays that he has traditionally had less weight in the series, missing most of Alpha, all of III and most of the Vs series, so it’s expected to some extent that he’s ignored by Capcom even if it is a dumb decision.
Chun Li, on the other hand, has always been there, Capcom will have her sell dozens of slutty alternate outfits, put her in every crossover, have her sell thousands of merchandise, have her drive the story as the third character with the most screentime in ASF after Rashid and FANG, but when it comes to beating her nemesis they throw her away in favor of Mr. NoStory, the greatest hero. Of course fans of her character complain. Capcom did not forget about her like they forgot about Guile; they used her. They feel much more comfortable with a Chun Li that needs to be rescued twice per game.

Ken’s fans don’t care about him being almost invisible
See, Ken was one of the most likable characters in ASF, together with Rashid and Zangief, and it would have been cool to have him do something in the last Act, but, in all honesty, I feel he was treated fairly* in a story that was not about him or about Ryu*. He did his stuff, he was great at it, and that’s that (if anything, Ken’s story got hamstrung by having him waste his time driving Ryu’s character, what a surprise, so you know what character to blame for Ken’s role). Ryu’s role in this story should have been similar to Ken’s, with the addition of fighting Necalli if you will. They had no storyline business here and that’s why the final fight against Bison was so lacking. Ryu was there like, “Uhmm… I’ve been told I’m the hero and you are the villain… Shall I kick your ass without giving a shit?”.
The day Capcom makes a legit story about Bison hurting Eliza or Mel I might root for Ken to beat Bison, but for now I’ll keep rooting for Chun Li. Blame me for wanting heroes with a story.