Pokerstove is an (admittedly imperfect) but invaluable tool for this sort of analysis. For example, let's suppose that the only hands you play are pocket pairs, all broadway suited, and AK,AQ,AJ,AT,KK,KQ. Not counting blinds, that's 13.4% of all hands. Assume the opponents play all of those but add in anything with an ace in it and anything where both cards are T+, and all suited connectors. The villains are playing 30% of their hands (discounting blinds).

Pokerstove (again imperfectly) will tell you that with 5 players to the flop, you are going to win 25% of the hands rather than the 20% you'd expect.

The problem with pokerstove is that it assumes all players play out all cards. In real life, you're going to be executing a better betting strategy to ensure that when you win, you win larger and when you lose, you lose less. You have to take Pokerstove's numbers for what they are and not try to make them into some sort of crystal ball.

An example of this is where pokerstove calculates that AA is a winner 52% of the time. In real life, of course, AA is a winner ~75% of the time. The reason for this (I think) is all the folks who played 22 and didn't improve on the flop folded against you're continued aggression. Some of the folks who had a pocket pair folded preflop and in fact would've gotten their set on the flop.