Can 5 wild cards be used as 5 aces in a 7 card game?

Yes, when playing with true wildcards a five of a kind can be formed. This is the highest valued Poker hand.

The question however alludes the existence of wildcards which don't allow five of a kind. There is such a thing known as a bug, which is a limited wildcard. Usually bugs can only be used to complete other hands, like a straight. In such games this bug can not be used to create five of a kind.