@numair: .deb is actually just the wrapper (used for jailbroken iphone apps). The binaries (executables) inside them are completely different from the ones used by N900. So, no, they're not compatible with one another.

But if there's any particular app or games that you would really like to have on N900; why don't you write to the developers (there should be a link to them in their respective appstore pages) and see if they would consider porting their apps to N900.