Well, if you ask *me*, DAI Cullen looks nothing like Cullen in DAO. Zevran looked nothing like in DAO in DA2. Alistair I only recognize from the name. And so on.... 
Agreed, it bothers me too. DA2 Cullen at least looked like a handsomer version of DAO Cullen (which makes sense; some people grow into their looks), but out of nowhere DAI Cullen looks nothing like DA2 and DAO cullen except the short curly blond-ish hair (not even the same shade anymore)! While BioWare does change characters' complete facial structure from game to game, they were on a roll with Cullen and then switched out the old ball for a new one. WHY??!!
Speaking of which, I don't really like their tendency to change some characters' facial structures between games. Like Cullen, DA2 Leliana looked almost exactly like DAO Leliana, then they randomly gave her a whole new facial design in DAI. DAI Varric looks exactly like DA2 Varric, but DAI Cassandra looks nothing like DA2 Cassandra except being a pale human woman with short black hair and smokey eyeliner. Alistair just keeps getting hit harder and harder with the ugly stick every game (to me), yet Morrigan looks exactly the same except from previous games except ten years older.
... I hope they don't do that with Solas. I like the way he looks. It perfectly suits his personality and overall demeanor (cool, aloof, a bit wistful to be somewhere else, a bit wild and feral without being savage or dangerous). I would hate it if they decided to randomly give him a completely new design unless there was shown to be a story reason, like Flemeth's change from DAO to DA2 (though only revealed in DAI). Unless his change in appearance has something to do with being an elven god - the ability to shapeshift, his current form in DAI turning out to be a disguise, his form changing as more of his hidden nature is revealed, etc - I don't really want him to change. Like Morrigan (the other proud forest apostate), I want to see him as he is in future games. ='(