Metal Gear Solid shouldn't really be on that list- 2 & 4 were good, albiet flawed, games but 3 is the best of the lot. Bringing back BBoss though was retarded. Plus MGS is already the third in the series..... in fact those examples you chose were odd as Empire Strikes Back, Aliens & Terminator 2 are the best of the bunch and are all sequels.

It's true though that on the whole most sequels are more 'Bride of Chucky' than 'Bride of Frankenstien'.