Favorite sequel in a series

The game that was your favorite or had the biggest change in a series that made you like the series.

Not sure if this counts, but I'd probably say the new XCOM. Since XCOM was an established brand, there were tons of expectations on it. And I think it lived up to it's legacy. But I wasn't an old player from back in the day, I'd only just played old XCOM the same year the new one released. And it had a lot of great things about it, but some clunkiness due to when it was released. I thought the new game pushed the series forward into the modern age with respect to it's roots, but also with a dedication to make it less impenetrably difficult to get into.

I'll base this strictly on game that came out this generation:

Mass effect 2 vastly improved the gun-play of the first, and although many disagree with me, also the writting to some degree.

Uncharted 2 completely surprised me. I liked the first game, but it was indeed slightly unpolished. The sequel was such a vast improvement that it was hard to fathom.

Assassin's Creed II. The first one, while did have a couple of great mechanics and ideas (especially the fantastic free-running system), was fatally flawed - it was repetitive as hell. Here, game player, are seven dudes that you should kill in these seven missions, and to complete each one of those, first you'll have to finish three side missions of which the most interesting one is pickpocketing. To be honest, I didn't finish the first Assassin's Creed as I got sick of it. The sequel, on the other hand, was fantastic - the story and characters, the improved fighting mechanics, the amazing scenery, and, what's most important, an incredible amount of side activities and varied missions. Assassin's Creed II defines what a proper sequel should be.

UNCHARTED 3!!!

This is strange considering my initial playthrough had left me disappointed. My hype was through the roof and it did not meet expectations. I started up another playthrough about 5 days later out of sheer boredom and found myself better able to enjoy the game. About a month an a half after its release and having completed the game 3 times I could safely say that I preferred UC3 over UC2.

I popped in Uncharted 2 a few months ago, did another playthrough and upon completion I felt justified in my opinion.

The Legend of Zelda: Ocarina of Time / The Legend of Zelda: The Wind Waker - Ocarina of Time ushered in the 3D Zelda and pretty much defined the series as it is today. Ocarina of Time was definitely the most influential game in the series on where it stands today. However, Wind Waker was my personal favorite game in the series - the characters were my favorite, I enjoyed the story the most, and, as proven by the HD re-release, the look of that game truly was forward-thinking and timeless.

Silent Hill 2 & Silent Hill 3 - Silent Hill 2 is what took the series to new heights. As a fan of SH1, I enjoyed Silent Hill 2 and Silent Hill 3 equally. Silent Hill 2 had the deeper story and really showcased complex mature themes, while Silent Hill 3 perfected the visual presentation and was a excellent direct sequel to SH1, SH3 also had my absolutely favorite protagonist of the series. The third game was the last true Silent Hill game imo, since it was the last game where the two most instrumental members of Team Silent - Masahiro Ito (the guy who designed the look of the series) and Hiroyuki Owaku (story creator of SH2 & SH3, co-writer of SH1) worked directly on. It was also the last game that had the true Silent Hill feel. Silent Hill 3 was supposed to conclude the core series, since it has an ending that brings proper closure to the story-arc that encompassed the trilogy of SH1, SH2, and SH3, also Masahiro Ito stated that in the mind of him and Owaku, that the Silent Hill story was over after SH3. Before they were disbanded, Team Silent delivered three critically acclaimed games (going by the Metacritic avg in the mid-high 80's)....with SH2 perfecting the approach to themes and story presentation and SH3 perfecting the look.

Uncharted 2 - The first Uncharted was very good, but it was Uncharted 2 that made the series a top name in the industry and one of the absolutely best action games ever released.

Resident Evil 2 - When I think of "Resident Evil", as in the survival horror series, I think of Resident Evil 2. RE2 perfected the formula. It had great A and B scenarios that presented the events from different perspectives. Don't get me wrong - RE4 was excellent and one of the best action games ever, but it clearly took the series in a different direction - a direction that could be argued it what led to the series being lackluster with recent released. RE remake on GC was also great, but it was RE2 that I think really made the series the survival-horror household name and introduced the series best characters like Leon and Ada.

Grand Theft Auto: Vice City - imo the best GTA game to date. Everything about the game was great, it took the 3D approach to the series that GTA III brought to new heights, while also delivering great atmosphere, the series first talking protagonist, and the best soundtrack in the series to date.

God of War II - The best game in the series imo and one that really captured the height of what made the series great.

Mass Effect 2 - The height of the Mass Effect series.

Super Metroid - The game that not only came to define the 2D series, but also the term "Metroidvania".

Metroid Prime - Even though it was it's own internal series, it's still part of the Metroid series. Metroid Prime took brought the series into 3D with style and to this day is one of the greatest and most critically acclaimed games ever made.

Zone of the Enders 2: The Second Runner is the single best sequel to a game ever. It shows how sequels should be done… improving on every single solitary aspect of the previous game, also adding new elements, and balancing that in such a way that the game retains familiarity for existing fans.

uncharted 2 among thieves : even though the first part was great, but when the uncharted 2 came , it was jaw dropping !

Legacy platformers such as Sonic Adventure 2,Sonic Advance 1, 2 and 3, along with Klonoa 2. There's way too much to be mentioned in my mind right now

@rekten87: The first time I ever heard the term "Metroidvania" was when Castlevania: Harmony of Dissonance was reviewed. And considering that Symphony of the Night(the first non-linear entry in the franchise) hadn't been released when Super Metroid was released, your claim is absolutely false.

@Hell_Dude: The story was fantastic in Assassin's Creed 2. But gameplaywise, all they did was take an original idea and throw it mostly out the window in favor of GTA-style progression. If it hadn't been for the announcement of AC: Brotherhood's multiplayer mode, I never would have played the series again.

For me, my favorite sequel of the generation wasn't part of a series(since to be a "series" you need at least 3 entries). Mercenaries 2: World in Flames proved that you could make a direct sequel to a last gen game and improve it simply by making it bigger.

First one that came to mind for me was Burnout 3: Takedown.

Burnout 1&2 were fun racing games. Takedown might be the greatest racing game ever. Game did so many things right, improving from the previous two. The speed, Crash mode, dead-on controls and even online multiplayer. Everything a fun video game should be. Accessible, polished, and an absolute blast to play.