Immersion is a hoax created by developers to justify points of laziness or personal preference. What matters is that a game knows what it's trying to do, does it well, and can be enjoyed the way it was intended to be enjoyed. An art style that properly reflects that intention or tone is a good thing.
Ask yourself: You still enjoy animated films, right? Disney and Pixar's classics are still classics, with some of the best characters, stories, and visuals cinema has seen. Why should a crazy, cartoonish art style in a GAME put you off any more than it does in a film?
I feel the stubborn attachment some people have to "realism" is childish. Don't get me wrong, I greatly respect people who can pull off realistic visuals in a game, but remarkable visuals are remarkable whether they're realistic or not, and developing a consistent, intentionally stylized art style is no small feat, and I respect that too and, in a lot of cases, enjoy that more.
Except Borderlands. But you know why I don't like borderlands? Because I think it's ugly and don't LIKE the art style, or the gameplay, or the writing. That's all there is to it. I just don't like the game. I'm not going to pretend it's "immersion-breaking" and hide behind that as an excuse to somehow make my preference seem objective. I know a lot of people who love it, and with just as many good reasons for loving it as I have reasons for not liking it. And I accept that, just as much as I accept that others like Call of Duty while it just isn't my thing.
I really wish the gaming world were able to take that attitude more easily. It seems like we're always wound up in some struggle for objective legitimacy in everything we do now adays. We can never just play, we have to somehow justify it. We can never enjoy the games that we enjoy and just call it at that, we have to argue why our games are better and why other peoples' games are worse. We gotta cut this crap out and just relax and enjoy ourselves.