It just annoys me that Solas gets a dishonorable mention but not, I don't know, Anders? And Isabela (although I do like her) contributed to the sacking of Kirkwall for purely selfish reasons, and she gets a place in the top. So yeah, I also got the feeling they were either more familiar with DA:I or at least greatly preferred it to the previous games.
Given how hated Anders is by the fandom, it's possible he didn't even make it on the "most popular character" honorary mention list because not enough people liked him enough to vote for him. =/
Solas being counted among the honorable(ish) mentions tells me enough people liked him enough to vote for him, but the "dishonorable mention" part was added by WatchMojo because they personally didn't like him, and/or to appease the Solas haters.
Wait - Cullen beat out Solas? Cullen beat out anyone besides, like, Blackwall?
Was the contest about which character best resembles white bread?
EDIT: Watching the video, I'd say it's more that whoever put it together has an obvious penchant for the light-hearted roguish type. (Isabela, Bull, Sera, Zevran, Dorian, and Varric all fall under that heading. You could make a case for Leliana, especially in Origins. Even Shale's more comedic than complex and emotional.) If you ask me, the only characters on that list that deserve to be there are Morrigan, Cassandra and Varric (And Varric at a much lower position.). Don't know what's up with the dishonorable mention though. Is it because Solas is an antagonist? Because he's more controversial? What's the criteria there?
...And seriously, Cullen?
I'm not really surprised about Cullen, considering he's had legions of fanboys and fangirls since the first game, and his popularity has been steadily snowballing each game, culminating in the most sickeningly sweet romance with a sappy wedding and goofy dog and overt "happily ever after" ending to date.
Come to think of it, I forgot that most video game players are "casuals." That is, they tend to play the video game once when it first comes out, then forget about it until the sequel comes. Then they play that, then promptly forget it. I mention this because my boyfriend and roommate are like that. (Dedicated fans like us are more rare than we like to admit.) Now that I think on it, most of WatchMojo's voters have probably played DAI most recently since it's the most recent game, so DAI characters are the characters they remember best, so they just voted on the first to pop into their head instead digging through their memory back to companions from previous games. Just my guess.
You definitely make a good point with "light-hearted roguish types," which I hadn't considered before. That definitely makes up a lot of DAI's roster, and explains the only companions from previous games (besides Cullen, Leli, and Morrigan) who made the list. (Shale, Isabela, and Zevran.)
Dishonorable mention: I think that's just the writer(s) of WatchMojo not liking Solas and being a bad sport about how much love he gets, but it might also be because he's been revealed to be an antagonist, and/or to appease the Solas haters since he's such a divisive character.