Well I'm know I'm late for the party, but here goes nothing:

Bioshock 2: this Levine-less sequel is the greatest cash-grab sequel ever made! It's was made by people who really love the original story and put tons of effort into into the sequel's. But it ultimately felt fruitless thanks to glaring plot holes. Other elements of the game received minor improvements, and it was pretty fun overall except the horrible final sequence..!

Dead Space 2: After the masterfully paced Dead Space, Dead Space 2 embraced the word "more" like most sequels do. This resulted new enemy types that didn't fit well with old ones nor the game's nature, some of new weapons ranged from useless to ridiculous (a sniper rifle in DS? please..) and some elegant yet "meh" cinematic sequences. Oh and let's not forget the game's fondness of happy-acid-shooting mobs and it's annoying habit of spawning mobs from nothin' right behind your back (although that was easier to tolerate on PC thanks to faster turning speed). Not to mention the final chapters where you get stalked by an invincible mob among an infinite swarm of fanatic Leapers. Finally, my personal nitpick: the game was too damn long..!

There I said it, now where's the buffet?! :P

mercenaries 2. uhgg

tales of symphonia 2. horrible game.

Manhunt 2

Dragon age 2 was a big disappointment, galerian ash, secret files 2, blood 2 and yes still life 2 was really bad cant even finish it..

Luckily I can think of a lot more good sequels than bad ones

so who was the killer?  i will not be playing this game based on this review, but was left hanging after ST 1.  I accept Spoilers!

I really wanted to find out who the killer in Still Life was . Only one person saw his face and that poor schlub got knife across his throat a second later.

Anyway, there are a ton of bad sequels I could pick but I'll say Dino Crisis 2. It's not a bad game as such, it's just completely inferior to its predecessor in every way. And Dino Crisis 3? Jesus.

The list is endless really... But to name just a few: Bioshock 2, Condemned 2, Dead Space 2 & 3, Dino Crisis 3, all Silent Hill games after 4, RE4, RE5, RE6, FEAR3, Wipeout Fusion, Uncharted 2, Oddworld: Munch's Oddyssee & Stranger's Wrath, Perfect Dark Zero, Mafia II, Clock Tower 3, etc.

Still ticked off with Resi 6. All the comments they made on the build up that it was going to be more like Resi 4 and then they release that garbage...

Alundra 2. Bet you didn't see that coming.

Call of Juarez: the cartel! One of the worst sequels in the current generation.

Fallout: New Vegas is this.

Every game released from 2002-2009 whose title includes the words "Sonic" and/or "Hedgehog".

Also, Marvel Ultimate Alliance 2. Don't get me wrong, I still really enjoyed it, but it's clearly inferior to its predecessor. Whereas the first game opened up the toybox that is the Marvel Universe and let the player frolic through 50 years of lore all combined into one enormous reality-shattering event, the sequel chose instead to focus on a single, recent paradigm-shifting storyline from the comics (namely, Civil War) - and then proceeded to gut and butcher both the source material upon which it was based and the RPG elements that made the original (and the X-Men Legend series before it) more than a mindless button-mash.

They had all the ingredients necessary to make an amazing licensed game, but they went overboard on the sugar and forgot to add the yeast. In the end, while still a total trip for fanboys like me, Ultimate Alliance 2 felt like one big missed opportunity - and a whole which was considerable less than the sum of its parts.

sequels that sucked... hm, I only know that dmc5 really sucks but it´s not an sequel. dmc2 kinda sucked.

the sequel of Final Fantasy XIII really sucked.

the sequel of Final Fantasy X sucked, ffx-2 was a way too commercial and almost meaningless... it became a cult none the less.

I could say that american mcgee´s alice madness return as a sequel had disappointed me a litte. due to camera angle problems the game became tiring very soon. The gameplay was rather for a pc game than for ps3, for ps3 it wasn´t fluid enough. All in all Madness Return was good yet could have become a better sequel, I believe.

Many people said mgs2 was not a goos sequel because of Raidens main role haha... I love Raiden and MGS2 too. So I wouldn´t agree to that. (The new Metal Gear with Raiden really sucks due to dumb dialogs but that game is not an sequal either... hm. Just had to mention it.)

Yeah right. I was also really disappointed, Stilllife2 was a real let down. 

BTW, glad to  see more adventure gamers here in GS:D

Devil May Cry 2... :(

Poor sequels are always a bummer, such a shame when you really love a game and rush to the next one only to be faced with disappointment. This mostly happens for me when the first game has one common complaint and the developer focus too hard on fixing that in the sequel to the extent they lose some of strengths of the first game. Key examples are Dragon Age 2 (a game I ultimately like but sucks as a sequel) and the terrible Force Unleashed 2. Force Unleashed 1 looked amazing and had a great story but was let down by gameplay, consensus was a sequel is a great idea because you fix the gameplay and you fix the game. They worked on the gameplay (I still don't think it was great but they clearly worked on it), but the storytelling was atrocious and everything else fell apart. Dragon Age: Origins is a masterpiece in my eyes, but on a presentation level (specifically graphically) it falters, and some found it overtly complex. In the sequel they sorted presentation in some ways, but went overboard on fixing things that weren't really problems and lost a lot of what made it special. Oh and then there are sequels like inFamous 2 and later Assassin's Creed games which just bummed me out in general.

Apologies for the long comment, really enjoyed the blog though. Clearly it got me thinking.