never slow play in omaha, never!

flopped quad 7s, of course i check, villain bets i raise he calls, turn as, river ah villain shows four of a kind aces ,me 7777 bummer! I still won the tourny tho

this is one reason i hate omaha so much

What does slowplay have to do with it though.

if he called your checkraise on flop, chances are hed have called if you bet out. Unless you wanted to go all-in or overbet, but then why would you want to do that.

By turn he has full house and no way hes folding.

its just how the cards went down....it happens

the 2 biggest rules in Omaha (especially Omaha Hi) :

1) never over-estimate a pair on your starting hand even a big one ( if you don't flop a set then fold it as quick as you can)
2) never slow play a good hand you hit on the flop (set but moreover straight, flush and so one) as it is likely that somebody on a draw will hit a greater hand on turn or river. As you don't want them to do so you have to discouraging them by betting hard : they should have to pay a lot for hitting their cards.

Your opponent feels strong enough with his pockets aces to call your raise (which was a big mistake). However he was lucky enough to hit both turn and river.
There is nothing you can do about that as as Alan said once he hits his third ace you even can put him all-in he would have called you.

PS : I forgot to say that your table position is also important at Omaha (but should I really need to say ... )