Overall the game is very good - whether it is better than Re 5 is debatable though, as RE 6 does suffer from various problems that it's predecessor didn't : Very problematic camera positioning (especially during Chris's penultimate level), dodgy controls (especially when running) and unskippable end credit (which last for around 10 minutes).
The 5 main characters missions are different only in how enjoyable they are : Leon's is the best, with Jakes being boring. Ada's one is good, except for an unforgiving timed sequence which gets very annoying, very quickly.
Graphics are good - detailing is good, but the usual gloomy surroundings does get annoying, although Jake's blizzard map is even more so.
It's worth getting, as long as you can get it as cheap as possible.