well, it is a failed if the new one is just an improved of the old.
Look at Roller Coaster Tycoon: the RCT2 is completely the same as RCT, just add some more things here and there, fix some bugs then boom. It's pretty disappointed u know. Rather than making it a making it a brand new version, it should be an extension, or a patch...
The first version of RCT sucked. So their newer versions should be drasticaly different if they wanted to have a good game.
If we are using examples, take grand torismo. It was an epic game in every sense. With each new version the graphics were improved, More realism due to better engine etc. New cars/tracks. Brilliant. They nailed it with the first couple of versions and therafter made improvements to try and make that game perfect.
The same goes with DW2 and 3 IMO. All they needed was to improve the graphics. Update the maps. More and better cutscenes. More troops in each battle. And shouldve went in that direction. Instead they decided they needed to change all of the characters completely, crammed in 100 new feautres. Changed the gameplay. They didn't try to perfect the great game they had. They just kept changing and adding things.