What you have to know:
Umbrella Chronicles is an on rails shooter. The game will take you room by room or area by area, for you to clear the opponents. You can move the camera with the nunchuk to attack enemies or pickup weapons, herbs etc. There are areas where there are 2 or 3 paths to take, you decide which one to follow. So you have some degree of deciding to which path to take (in some areas)
Game story is excellent, chapters are hard, so you will get a good challenge but it is do-able. Boss battles are great, need to find the weak spots to beat them. Graphics are very good for the Wii, sound effects and music are ok.
Takes a while to beat (took me 14 hours to clear it all the first time). There is a lot of replay value (3 difficulty levels), side quests, ranking improvement, so it is good. The ending is rewarding
I think in my opinion that is an excellent, must have game. I like it very much!!
Umbrella Chronicles and Medal of Honor Heroes 2 are two of the best new games (my opinion) beside Super Mario Galaxy right now for the Wii