Pfft. Underrated games? Let's talk underrated systems. The Wii's gotten more undue hatred than any other console I've seen so far and gamers this gen did miss out on many, many wonderful gems like these:

Xenoblade Chronicles
Fragile Dreams
Muramasa: Demon Blade
Zack & Wiki
Sin & Punishment: Star Successor
Trauma Center: Second Opinion
Trauma Center: New Blood
Dead Space Extraction
Dragon Quest Swords
Cursed Mountain
Klonoa
Calling
Resident Evil: Umbrella Chronicles
Resident Evil: Darkside Chronicles
Konami Rebirth Series: Gradius, Contra, and Castlevania (WiiWare)
.....& so on.

As for other non-Wii gems:

Trauma Center Under the Knife 1&2
Devil Survivor 1&2
Lux-Pain
Asura's Wrath
Child of Eden
House of the Dead 4 (PSN)