The best mech game is also made by the creator of MGS.
I still remember the limited days i spent playing this game. The graphics are amazing, i really enjoyed the cell-shaded and 3D environment. The world wasn't very immense but definitely suitable for the situation. The battle system in this game is out of this world. It requires lightning fast reflex if not, at least some crazy thumb movements. The weapons in this game are totally kick-@$$ especially the energy canon thing. Wow. The story is epic. Sound is pretty good too and accurate such as slicing other mechs and releasing large amount of energy from that canon of yours. I can't put words to describe this game. It's simply amazing. Go get your hands on it if you can.