My vote? Microsoft Combat Flight Simulator 3. First of all, the box stated a 400mHz processor under the minimum requirements, yet check any review and you'll see that people with computers up to 1.8 gHz have trouble getting the MAIN MENU to run smoothly. Secondly, it abandoned ALL the gameplay mechanics of the original CFS (which was one of my favourite titles of all time, I even bought one of the 3rd party aircraft packs). Component damage is not listed in real-time anymore (in fact, I'm not sure it exists), even the nimblest fighters handle like a drunk mule, and they completely changed the control layout with the new Flight Simulator engine. Add to that the apparent removal of airports (I didn't get far enough in the campaign to be completely sure, but the free flights can't start on the ground anymore), the inclusion of bomber turrets (yeah, because when I'm on a bombing run, I have time to fly, handle AA duty, AND drop the actual bombs. At once.), and broken RPG elements, and it just adds up to a horrible game.
Worst of all, though, was the inclusion of 'mission zones' (are these EVER popular?), where if you left a (small) area, even on 'free flight', you are yelled at by the computer. What happened to being able to fly _all the way around the globe_ nonstop, like you could in the original game?
Considering I picked up this relatively old title two months ago for $30... well, it's probably worth five. Tops. I trashed it within two days.
Other disappointments? Any 'tactical shooter' (read: three shots or one headshot is fatal to your character) where you have to protect your AI buddies. The only good Tom Clancy game is a solo Tom Clancy game.