I think the PSP Tactics Ogre: Let Us Cling Together is for sure the best of this genre I’ve ever played. I love SRPGs.
I am a sucker for Front Mission III, which plays more like a tank SRPG than a mech game:
I’ve tried FM4 and FM5, but didn’t really quite enjoy those two at the same level.
Keep hearing the N64 Ogre Battle game is very good. It’s rough to get past the visuals, but, I’m willing to give it a go.