Sequel Improvements

[gunswordfist]

What are your favorite improvements in sequels of your favorite (or not so favorite) video games? Whether they created improvements that are present in all the following sequels of the series or are just featured in one of its titles.

I go first:

Sonic The Hedgehog 2:

-Tails
-Spin Dash
-Started the trend of Sonic going into space.

Sonic 3 & Knuckles:
-Use level select for each level you have beaten on/with multiple save slots. So many games should be ripping this off. It's perfect.
-Sonic's elemental shields
-Knuckles

Max Payne 2:
-Infinite Shootdodging
-Bullet Time system that slows down time even more based off of number of kills.

[Spark Of Spirit]

Mega Man 2 - Everything

Sonic 3 & Knuckles:
-Use level select for each level you have beaten on/with multiple save slots. So many games should be ripping this off. It's perfect.
-Sonic's elemental shields
-Knuckles

Not to mention:

-Tails can fly, swim, and even carry Sonic!

[gunswordfist]

Mega Man 2 - Everything

Sonic 3 & Knuckles:
-Use level select for each level you have beaten on/with multiple save slots. So many games should be ripping this off. It's perfect.
-Sonic's elemental shields
-Knuckles

Not to mention:

-Tails can fly, swim, and even carry Sonic!

:DOh yeah!
Mass Effect 2 - Everything, except the story is only good for getting to know Cerberus since everyone can die....and most of the game is about recruiting characters. Oh and only getting to fight the Collectors 3 times and the fact that you only get to save one colony from them also sucks.

[Dr. Ensatsu-ken]

Ninja Gaiden 2 (NES):

-Ryu can now climb walls
-Clone Ryu power-up (WHY the hell has Tecmo NEVER brought this back in ANY Ninja Gaiden game?)
-Stage based hazards (i.e., wind, black-outs, etc.; once again, WHY has this never been brought back?)

Donkey Kong Country 2:

-Being able to throw your partner Kong as a projectile
-Dixie's gliding ability