Except in some European casinos, which don't check for dealer blackjacks before play. Under those rules - someone may correct me - a blackjack outranks any other 21, and if the dealer has a blackjack and you made a 21 with more than two cards, I believe it's not a push and the dealer wins. I could be wrong, it's been awhile since I played over there.
They often weight the rules back towards the players in other strange ways, like, being able to double down at any time (even on the 3rd or 4th card), resplit aces, as well as surrender.
