The replayability is good, but to be honest, I'm getting kind of tired of it. Farming for cash just gets boring after awhile. Using infinite weapons removes a lot of the fun as well. Searching for emblems is more of a chore than anything else, considering some of the ridiculous locations for them, and I don't want to use a guide. Not only that, but most importantly I found myself getting bored of the level designs far faster than I did with RE4.
I still think it's a great game. But, at the same time, you have people who play through every chapter in every difficulty, collect all the treasures and BSAA emblems, upgrade all the weapons, unlock every bonus feature, play the shit out of Mercenaries, and still say that they're coming back for more. In my case, I just can't see it. The game's fun factor just isn't as long-lasting for me.