Dragonball Z has Budokai 3.
Gundam has SD Gundam G Generation F, G Generation SEED, G Generation Advance, and Mobile Suit Zeta Gundam vs Mobils Suit Gundam, all of which imports.
In fact... Several mecha series are part of a series called Super Robot Wars, which totally rocks. Find SRW4 on a website, and then buy alpha and alpha gaiden for the PSX, alpha 2 for PS2, and MX for PS2. Great games. xd
In general, games based on animated stuff, be it American or Japanese, tend to be little on the poor side. However, there are always exceptions to the rule, including DBZ: Budokai 3 (PS2), DB: Advance Adventure (GBA) and the Naruto Gekitou Ninja Taisen series (GCN)