5/5
http://ps2.gamespy.com/playstation-2/ratchet-and-clank-up-your-arsenal/562785p1.html
Ratchet & Clank: Up Your Arsenal is a very good single-player game, but the addition of a fun and feature-rich multiplayer aspect really pushes it beyond its predecessors. It was a bold route to take, but Insomniac has executed with perfect grace. If this is the last Ratchet & Clank game for the PS2, then the series will certainly have gone out on a high note.
Ratchet & Clank: Going Commando was an excellent sequel that made definite improvements over its somewhat drowsy predecessor, and now, likewise, Ratchet & Clank: Up Your Arsenal makes marked improvements over that second game. Combining a solid single-player adventure and all-new online competition modes, Up Your Arsenal is clearly Insomniac's most impressive outing yet.
http://ps2.gamespy.com/playstation-2/ratchet-and-clank-up-your-arsenal/562785p1.html