I'd say that any series that sees more than two releases in one generation is over-saturated.
Halo: Reach will do it for that series, unless it's a radical departure from previous Halo shooters.
Mario is pushing it pretty hard, since there are already 3 released or announced Mario platformers for the Wii. There are a lot of game design differences between SMG and NSMBW, so it's okay for now.
Call of Duty is there, the only saving grace being that it alternates developers and settings, and the usual offenders of rhythm/music games and sports games are there.
"The worst part about these reviews is they are [subjective]--and their scores often depend on how drunk you got the media at a Street Fighter event." — Mona Hamilton, Capcom Senior VP of Marketing
*Image indefinitely borrowed from BrainBoxLtd without his consent.
