It's like how people drool over SC2, but compared to SC4 it doesn't stand the test of time. SC2 was probably more well received in it's time, but SC4 is simply a more fun game with greater depth.
MvC3 will be getting patched I suspect march 15th with the DLC unlock. 2 infinites have been found and people are making x-factor-less 100% combos with only 1-3 meter. As well a lot of these combos meet their corner only requirement by carrying them pretty far horizontally before needing to do the necessary OTG relaunch shenanigans.
As for sentinal other characters can do the damage he does, they just have to put more effort into maxing out the combo damage. The bitch with sentinal is he only needs a few hits to get the damage, but really anyone can turn an L attack into sentinal damage if they keep the combo active...I know C.Viper sure can (1meter 100% combo wtf?!?)!