Huge fan of old school G'man. Godzilla: Final Wars should be good stuff. It doesn't get any better than 10 monsters beating the piss out of another.
Watching Godzilla on Saturday mornings was a huge part of my childhood. Old school, I'd say Godzilla vs. Megalon is one of my favorites. I really like the of Megalon and Gigan. Plus its got a giant robot in Jet Jagua.
New school, the recently released on DVD Godzilla, Mothra, King Ghiodorah: All Monsters Attack is probably my favorite.