WARNING - THE POST BELOW CONTAINS VOLITALE FLAME FUELLED MATERIAL. THERE WILL BE NO CAKE IF THESE ARE IGNITED.
Seeing as everyone's mentioning everything, I'll go ahead and mention what I think either doesn't deserve a sequel, or didn't deserve a Sequel.
- EVERYTHING Terminator related after Terminator 2 came out, with the possible exception of Terminator

awn of Fate. T2 closed the franchise together with the kind of plot knot tying that makes MGS4 look passable. Fast forward - now we have Sarah Connor Chronicles, Terminator 3, Terminator Salvation, a slew of Movie tie ins...the only reason I spare Dawn of Fate is because it works as a prequel rather than a sequel (the main plot concerned getting Kyle Reece to the Time Machine).
- Avatar. James Cameroons Avatar. First off, thank you Cameroon for releasing a variety of Internet Nazi that makes Blizzard Trolls look tame. Asides the fact that the movie has no substance and it's lazy designs yadda yadda, Cameroon has indirectly caused people to commit suicide shortly after seeing the movie. Between this, the deranged loonies in America trying to be registered as an ethnic group and the Avatar trolls likely to flame me, it's no wonder The Hurt Locker won the Oscars instead. Asides, making a sequel I feel is an insult to those who had their loved ones kill themselves over the first. Even then, it won't be involving everyone's favourite Catgirls, so it's likely the already infamous trolls will reach new levels of trollishness.
God that was longwinded ^_^
- Metal Gear Solid. Same reasons as my notes on Terminator.
- The C&C franchise. Anything EA has made to date is just...well, it rapes the name, and it shows. Generals was good, but it wasn't a C&C game - it was EA slapping a brand name on a shiny new product that otherwise might not have sold. C&C 3 was an unbalanced mess, and is so canatonically wrong it makes the C&C Wiki look cantatonically accurate (which is some feat). Red Alert 3 completely missed the point of the Red Alert universe, turning an otherwise humerous universe into what can only be described as "A mix of lolcats, racism and crack" by my roommate. Lastly, C&C 4. They could really have revitalised things here, but they do bugger all with any of the gameplay concepts. And the story...it makes me want to retcon C&C 3 and write my own horrible fan fiction.
- All the WoW addons. Charecter Derailment, plot yadda yadda asides, when are we going to see a Warcraft IV? Will we ever see a Warcraft IV?
- Left 4 Dead 2. I was going to boycott this...then my father got my brother it for Christmas. I wanted to hang myself. So I ended up playing it, and...it's the same, only more racist. Everything I knew would happen was present - it's just DLC on a disk.
- Portal. Now it's already known I hated the first one, but seriously, Portal 2? It seems they're doing it just for the fans.
- Speaking of sequels just for the fans, I have rather mixed feelings about Starcraft II. The Campaign is pretty good, and certainly replayable, but the plot for the Wings of Liberty arc is just...ugh. It's so...generic. Gameplay wise, it's more or less the same, but it at least doesn't take forever to crank out a single useless grunt by the time some Korean Zerg Rushes you.