Note that both apt-get and aptitude, together with dpkg, are part of APT (advanced packaging tool), which is the suite of tools handling .deb packages.
While I'm at it, neither apt-get nor aptitude are simply front ends to dpkg - both have fairly complex (and different) policies for how to handle dependency conflicts, etc, while dpkg makes you do everything by yourself.
Honest question, I haven't used an RPM-based distro since a couple of years ago. Last was opensuse 11, then fedora 3.
rpm is a pretty great format, but the frontends are not very good. apt, on the other hand, rocks, and aptitude rocks even more.