compared to 5 it depends on what you want. 5's presentation is better(cutscenes, visuals) and its got a few better mechanics(weapon switch and inventory management) along with much better replay value(RE6 ditched sp costumes, weapon upgrading and storage/buying). 5's design is also more consistent with what youre doing.
6 tends to be better than 5 in several ways. its story and characters are more involved, its more diverse in nearly everything youre doing/fighting/seeing, mercenaries and the online modes are better. its length is atleast 3x longer. Combat is much more indepth and offers a greater degree of freedom. it lacks 5's replay value, but makes up for it in sheer volume. Plus the AI wont get you killed now(usually).