Series with biggest leap in quality from one entry to the next?

Ha Dmc2 good one.
I really do wonder why they never made a 2 though....
 
And the one that came to my mind was assassins creed.
And for me currently the biggest one. It made the good concept actually enjoyable instead of boring.
Others might have had more influence but.. i also think their predecessors weren't..'unfun' so to say.

" Assassin's Creed -----> Assassin's Creed II was pretty radical in terms of quality.  A lot of the repetition was taken out, but on top of that, the storytelling was magnificently handled. "

Dawn of war 1 to Dawn of war 2.

" GTA 3-GTA4? "

Fifa 9 ---> Fifa 10

" Fifa 9 ---> Fifa 10 "

Leap backwards I would have to saw Dragon Age 1 to Dragon Age 2, and Dawn of War 1 to Dawn of War 2. In Dragon Age's case they destroyed so much of what made the first one one of my favourites, and with Dawn of War I just hated how they basically made it a Diablo style RPG instead of an RTS. 
 
As for leap forward... I guess what City of Heroes is today compared to what it launched as, but I suppose you could say that about any MMO if given enough time. 
 
I can't really think of any game that I felt improved by leaps and bounds over it's first one. It's always just felt like more of the same to me, in a good way, or they changed all the aspects I loved from the previous one to the point that it has none of the things I liked about the first one any more. 
 
I guess Red Alert to Red Alert 2, but it wasn't so much made better as it was just a different game that I ended up enjoying just as much as the first one.

" Dragon Age 2 -> Dragon Age: Origins "

GTA 2 to 3, 3 and Vice City to San Andreas, San Andreas to IV 
 
splendid

How the hell no one mention Battlefield 2 -> Battlefield 3 yet?

KILLZONE to KILLZONE 2

Windows Vista -> Windows 7

Killzone to Killzone 2 was pretty huge.

Mass Effect to Mass Effect 2 
 
@Three0neFive said:

"

                    Dragon Age 2 -> Dragon Age: Origins

                   

                "

I see what you did there

BC1-BC2.  

Jak n' Daxter ---> Jak II
 
And RE -->RE4, I really like RE4. I kinda like RE2.

Mass Effect 1 to Mass Effect 2.

Uncharted to Uncharted 2.  
 
I think it's under-recognized just how much less polished UC1 was.

" How the hell no one mention Battlefield 2 -> Battlefield 3 yet? "

" Fifa 9 ---> Fifa 10 "

" Dead or Alive 2 was a huge step up from the first game. I'd say the biggest is Resident Evil 4. To go from a series of poor games to one of the best games ever is quite the feat. "

" @KaosAngel said:

" How the hell no one mention Battlefield 2 -> Battlefield 3 yet? "

Probably because no one has played Battlefield 3 "

Mass Effect to Mass Effect 2. 
Or Uncharted to Uncharted 2

Empire: Total War to Total War: Shogun 2. 
I can't think of any counter arguments for this one. So I guess I win?

Mass Effect 1 to Mass Effect 2.

" @Ygg said:

"

                    @GetEveryone said:

"

                    Everything before Resident Evil 4 -> Resident Evil 4.  That game did so many things right and stands as one of the modern greats. I don't mean to say it's predecessors were anything less than stellar, but 4 really did produce a paradigm shift in the series' direction/quality.  5 isn't great, though.

                   

                "

4 wasn't the best game in the series and is ultimately why the series has became what it has; a shadow of its former self.  Yeah, it was a competent action game that made good use of the perspective, but it wasn't a proper Resident Evil game or worthy of being the next entry in the series.  The gunplay in 4 and 5 is laughably bad, enemies just bounce when you hit and kill them. Please, They didn't even bother fixing/improving the animation when you kill standard enemies.

                   

                "

Agreed. I thought 4 was a devolution if anything. Maybe the biggest RE jump was 3 to Code Veronica imo. "

" The last 3 Elder Scrolls games, and continuing to the next, every game is a huge leap forward. "

" @ViciousReiven said:

" The last 3 Elder Scrolls games, and continuing to the next, every game is a huge leap forward. "

I'd say Oblivion took more steps backward than it did forward. Not that it's a bad game though. "

A recent one would be Two Worlds -> Two Worlds 2

Call of Duty 3 to Call of Duty: Modern Warfare.  That was an astonishing leap.

" @FreakAche said:

" @ViciousReiven said:

" The last 3 Elder Scrolls games, and continuing to the next, every game is a huge leap forward. "

I'd say Oblivion took more steps backward than it did forward. Not that it's a bad game though. "

If backwards equals fun then I agree. "

AC1 to AC2 
It's hard to think they are both in the same generation.

" Empire: Total War to Total War: Shogun 2. I can't think of any counter arguments for this one. So I guess I win? "

" @SadPatrol

Mass Effect 1 to Mass Effect 2.

This. "

" @jorbear said:

" Empire: Total War to Total War: Shogun 2. I can't think of any counter arguments for this one. So I guess I win? "

No way, Shogun has a few welcome mechanics and tweaks, but the AI is still terrible and its still fairly buggy. Hell, the part where you actually fight dudes is exactly like it was in Rome Total war when it comes down to it.  "

"A recent one would be Two Worlds -> Two Worlds 2 "

"

                    Assassin's Creed -----> Assassin's Creed II was pretty radical in terms of quality.  A lot of the repetition was taken out, but on top of that, the storytelling was magnificently handled.

                   

                "

" The last 3 Elder Scrolls games, and continuing to the next, every game is a huge leap forward. "

" Doom 2 to Doom 3 "

Resident Evil 3 -> Resident Evil 4 

So many.
Uncharted 2>1
Assassins Creed 2>1
Just Cause 2>1
Killzone 2>1 
These are the first that come to mind.