I think the original Gamecube RE4 is a great game, within the context of its time. It still plays very well and graphically still holds up.
The Remake is essentially the same game with some tweaks and the graphics made over. It's a great game, but it's not the best in the series.
They should have gone to CV before doing 4 again, in my opinion. Again, CV is a great game within the context of its time, but it has dated, and probably only the most ardent of RE fans still play it. The scope of the original taken into the current gen could make it the best, if not one of the best in series.
RE9 relies too much on stylized gore, the main protagonists are not particularly memorable, the early sections with Grace focus too much on stealth and yet put in so many enemies you have to rely on a more confrontational strategy, which is hampered by a weak hand gun and a character who dies if the zombies so much as fart in her direction.
Now, sounds like I'm hating on it, and I'm not, but there are a number of elements that detract from this being a really great game, which is a shame, as it definitely had the potential to be better than it already is.
They tried to combine the best bits of 7, 8 & 4 and still managed to produce a game that is a lesser title in my opinion.