This.

Deus Ex to Deus Ex : Invisible War - just took everything that won awards in the first and threw it away

I was also dissapointed with Thief 2 to Thief 3 - much as it made a great media centre, the Xbox fell out of favour for me for being party to the messing up of these two titles.

More recently I was disappointed with MW2 vs MW

To a lesser extent I didn't like the change from fun, retro Resistance 1 (with the Chimera pursuing plan A, let's freeze the planet) to improved graphics but not so retro Resistance 2 (with the Chimera no apparently apply plan B, let's romp about in the sun with an unspecified plan and forget all about freezing the planet)

Seece said: Burnout Revenge - Burnout Paradise Don't like it going to Open world

that guy with the awesome new avatar is right !

This, I don't think it wasn't bad, I enjoyed it, but still:

Weapons, Multyplayer Online (modes, maps and.. well, basically everything), Campaign, Multyplayer Offline (up to 4 players), Fun: R:FoM>R2

Co-op: R2>R:FoM

Graphs (even tho R2 looks better, I personally preferred R:FoM atmosphere) and Story: R2=R:FoM

But the biggest disappoint to me in this generation was Burnout Paradise. Not an arcade racing game, no multyplayer offline = no good.

Crash Bandicoot 3 >> Crash Bandicoot: Cortex Strikes Back
Never been the same since it's PS1 days with Naughty Dog developing

Spyro: Year of the Dragon >> Spyro: Enter the Dragonfly
Completely crashed after Insomniac stopped developing, post PS1

S3&K => Sonic Adventure

C&C Red Alert => C&C Red Alert 2 (They made an awesome serious game too goofy)

C&C Tiberian Sun => C&C Tiberium Wars

Pokemon Red/Blue/Silver/Gold => Pokemon Ruby/Saphire

PoP 1,2,3 to 4 - first three, especially the second is among my all time faves, the 4th sucked monkey (*$&$#! was horrible gameplay, story etc etc

Halo:CE to everything that followed - nothing came close to how good CE was, especially not H3

and I have a bad bad feeling Max Payne 3 will take the same route :(