Really, it depends on the character.
Spider-Man I can live with his stuff being more Ultimate-based.
Deadpool better bloody be 616, because I don't want to see that "generic mutie hater" bullcrap again. Reading through those issues were bad enough.
Captain America, I like some of the ideas in Ultimate (a lot of parts of it were what I'd imagine would be like for a man from the 40s to wake up in the 00s), but some others were a little...off (the "France" comment espicially--it just doesn't make sense that a man who probably fought with the French during WWII would consider the people inheriently prone to surrender); so, a mix of both would probably work best.
And so on and so forth.