Should sequels or games within a series focus on refining aspects of the game or innovating?

They should be both innovative and refine aspects of the game. Some parts of a game may need improvement. Innovation is good for a series too.

For me, that depends on the length of time between sequels. Games should innovate when necessary. If a series persists with refinement over an extended period of time across several releases, innovation may be neccesary to revive flagging interest. Obviously, games should innovate if the prequel was released a long time ago, like a Kid Icarus sequel for example.

Refinement = expansion
Innovation = sequel

Refinement + Innovation = Awesome sequel

I think maybe the first sequel should be a refinement and then if it lasts a trilogy or longer it should be innovation every 2-3 games (like final fantasy).

Off the top of my head, Halo is a great example. Halo 2 was hailed as one of the greatest games of last generation and in reality the only thing it really did was allow masterchief to use both his hands and have online.

Halo 3 did exactly the same thing, touched up things and added minor additions (minor in the sense that it didn't change the way the game was played) and it was called over-hyped, even though it provided a better experience then Halo 1 and 2 (if you were to slap different names on each game and played them for the first time comparing them as competition, you would say halo 3 was the best).

I don't really care as long as the game is fun. Though, I wish some companies didn't try so damn hard to innovate. I miss the classic R6 and Ghost Recon series, before they went all hollywood style. In those cases, I wish they just refined the original gameplay style, rather than reinvent the franchises.

Some people will call refinements just cop-outs. I think innovation is needed with every new video game. It proves to me the developer's care about the game at least as much as money.

Innovation is not something you can pull out of thin air. You have to think how to innovate a game. Correct me if I'm wrong, but I'm pretty sure it was Hiroyuki Ito that came up with the ATB system in FFIV to FFIX and not Sakaguchi

A combination of both...

e.g I feel the Mario Series REFINES very well...but doesn't innovate much...SMG wasn't innovative...but it was refined so well it IS one THE best game ever made.

While you have games with MORE innovations:

e.g FF12 - here they innovated through the combat system....but the refinement wasn't great as it wasn't as great as the previous one