irmongoose is right - Logic is probably the closest in comparison, but now Soundtrack from Apple seems to be right in the ballpark as well - but I haven't used it, so I can't speak from experience. If they make an iApp version of soundtrack, that would probably be your best bet - keep watching, we may see one yet.
And doesn't MOTU make software too? I dunno...
I use CEP2 (now Adobe Audition) simply because our studio has a PC in it for the time being, and it will stay that way until lightning strikes, probably. CEP is pretty good, and provides a lot of bang for the buck.
Your other major editing option is of course Digidesign's ProTools, but then you're talking about REAL money.
<runs off to start a lightning storm>