A lot of people say this game is worse than RE5, and in some ways I agree. But it's mainly personal preference.. I think the demo is still available to download, you should try that before you decide whether or not you want to get it.
certain smaller elements are worse(no quick weapon switch, no weapon storage/buying/upgrading, unlockables for single player) which leads to worse replay value and it doesnt quite have that sheen of polish that 5 had. In most other ways i feel its better. Its diversity in what youre doing, the environments youre going through and the set-pieces/scenarios youre involved in are all much better and more diverse. Enemy diversity is much better along with boss designs. Youre control options are far greater allowing for more play styles(though the game doesnt do a good job of showing you everything). Its story/characterizations are also far better. You also dont need to worry about the AI this time around(for the most part) since they cant die now and they have infinite ammo. I kinda miss having to manage the ai's inventory and arsenal, but i dont miss sheva's ai screwing my over hardcore in the later chapters.
Youre also getting a LOT of content. Despite 5 having more replay value, 6's singleplayer is atleat 3x longer with a good amount of mercenaries content as well as many multiplayer modes. Overall i liked 6 more, but i do miss those smaller elements.
its fun and looks awesome, but once you use all the characters and kill all the enemies its kind of over. the one thing that can be said though is that the levels are LONG. you can easily spend 90 minutes on 1 of the 20 chapters or 2 hours if you take your time. its kind of weird how you'll beat a level and still want to play but then you realize you have to keep going for another hour after that