I am not sure about AoE2, but Warcraft 3 is not yet Intel-Mac native, and there is no perspective if it will ever be. This means that it will not run directly under OS X on an Intel Mac and has to run in Rosetta, the PPC emulator.
This *could* mean that the games may not run as good as you would expect or used to. Others can better on this, I'm sure, as I do not have an Intel Mac. But if you search through this forum, you will find a bunch of threads on War3 on Intel macs