Actually the games dos not stands on their own, in all witcher games we play as Geralt, a character from the books and without reading the books we can not understand this character better, why he loves Yennefer and not Triss, why is Yennefer special to him and he always end up with her no matter what. Of course in the games you can make Geralt love Triss if you want, in fact is a good thing that dev give us the choice because i admit Yennefer is not an ordinary hollywoodian tipe of woman, and some people don't like that. Triss is a nice character even if she has some ups and downs in games and a lot in books, but for me Geralt with no Yennefer in his live is not Geralt, is something else, but again this is only my opinion everyone is free to do what they want in the game. About Yennefer being a bad person and Triss a good person that is completely wrong, both have good sides and bad sides is all a matter of taste.
Quite a few gamers who are Yennefer fans disagree.