Silent Hill is the worst offender in that list IMO. FF has been pretty polarising lately, but many people loved XII, they fixed XIV and the XIII sequel isn't bad. They can still redeem themselves, but they must do it soon.
Other examples:
Tomb Raider (I know the last games are not bad, but it hit serious lows and it's still downhill from its origins)
Spyro
Crash
Possibly GTA. GTA IV and the expansions don't hold a candle to SA. BUT GTAV could be amazing (I believe it will be) so I think this will be out of the list eventually.
I'll post more if I think of any.
With AC; I would argue that it has actually improved. Let's be honest, the original was a turd. Even the spinoffs are much better than the original, and Brotherhood was better than II to many. III looks promising. This is actually an amazing case where a horrible game managed to sell millions and brought them back for a (MUCH better) sequel. I guess people realised the concept was great and gave the series a second chance.
No troll is too much for me to handle. I rehabilitate trolls, I train people. I am the Troll Whisperer.
