Not intending to offend anybody with these, as it's just in my opinion;
Gears of War - Poor story, dumb hypermasculine characters, repetitive gameplay and very short singleplayer. Gamespot gives it a 9.6... No way in hell. Has a colossal ammount of fanboys, most of which are probably 12 years old.
Rainbow Six: Vegas - It just wasn't a Rainbow Six game, just a GOW knock-off. Arcadey gameplay replaced any tactical shooter elements and singleplayer was just too linear. Once again, Gamespot gives a 9.1.
Resident Evil 4 - It's a game i enjoyed to a certain extent, but i didn't find it that good. I won't even critisise the story, dialogue or characters because Resident Evil just doesn't bother in any of those area's. Also, what happened to survival horror... RE4 barely had any horror moments in it. Some levels i found frustrating/annoying which made me very reluctant to replay.
Dead space - Combine RE4 and Event Horizon and you get something as bland as Dead Space. Not really horror either, just gorey and 'boo' scares. When i was bored with it's predictable linear gameplay i would play a game of my own wher ei would have to search exta hard for any moments in the game that might actually have any originality. I lost that game btw.
Call of Duty 4 - It's a competent game, but other than being set in modern war the gameplay it largely unchanged to previous installments. Linear, linear, linear, moving from one checkpoint to another where team mates will stand behind cover until you advance to a certain point. Singleplayer was pretty short too and wasn't actually that hard even on the highest difficulty.
F.E.A.R. - You've played five minutes of this game and you've pretty much played the whole thing. A simple FPS where you just kill the same enemies to ad naseum. The repetition in this game was just so painful that i only just managed to play it the whole way through. Not a good horror game either. Watching the same girl walk past then fade away get's old fast.
Half-life 2 - To a certain extent. The source engine is great and the singleplayer has it's moments. But a simple story, one-note characters and pretty repetitive gameplay that they try to mask just by throwing you into a new location every couple of minutes. It's still a good game but imo it's not 'best game ever' material or anything. Also, apart from Ravenhol it didn't retain much of the horror elements from the original. Speaking of the original, it's only a bit less linear than the original. Maybe i'll get into trouble about this because aparently your allowed to say Halo overrated (which i would add, had other's not already) but not Half-life 2. Hmmm... Anyway, i'm waiting to get flamed over this one.