Bleach is always a classic anime for me, sadly I'm not much of a hardcore-manga dude to read the rest of the story, as there are crucial points there (I'm aware what happened)
Anyhows Aizen is too OP , sadly the creator has a tendency with their other shows (Dragonball anyone?) yet I love how he was portrayed. The ego, ability, looks and just generally able to deceive many just made him a villain to remember.
The only downside is that the good guys never seem to die (please don't say Gin, doesn't count IMO) despite the numerous times excessive blood was lost from Ichigo, etc. The one character I hate for some reason (don't remember the name) is the one sucking up to Aizen.
Either way, I'd give Bleach an 8/10.