Yup BOB and BOB2 are wonderfully immersive sims. I remember rushing to the store to buy the first (back when you could still buy sims in retail stores). Been playing it and the sequel ever since.
The new AI is un-freakin-believable. And the campaigns have to be seen to be believed. The huge number of aircraft in a raid is staggering. You really get that "holy crap am I gonna get through this alive?" feeling. Nothing quite like flying into hundreds of bombers plinking at everything with a black cross on it, hoping to get out in one piece. And quite often, you won't.
You can't really compare BOB2 and Il-2. BOB has the better FM and AI, but Il-2 has the entire war to fight in. BOB is obviously limited to, well, the BoB!
Graphics wise, it's a toss-up. BOB's clouds are much better IMHO, but I like the landscape in Il-2 better. That's just a personal opinion as the landscape in BOB is very detailed.
I like both, really...for different reasons.