Overrated
Grand Theft Auto (most overrated crap ever made)
Mortal Kombat
Spinter Cell
XIII
Anything made by Ubi Soft
Final Fantasy VII
Final Fantasy X-2
Rainbow Six games
Soul Caliber series

Underrated:
Phantasy Star II and IV
Phantasy Star Online
Halo 2 (Yes, this game is underrated)
Final Fantasy VIII
Xenogears
Suikoden series
King of Fighters
Street Fighter Alpha series
Guilty Gear series (thanks alot, Sony asses)
SNK Vs Capcom: SVC Chaos
Virtua Fighter 4
Garou: Mark of the Wolves
Any of the Sega Dreamcast games