They should listen to what their customers want.
For example, many Sonic the Hedgehog fans have been begging for a Sonic game with absolutely no innovation whatsoever, just pretty graphics and genesis-era gameplay. Sega acted ridiculous by announcing that Sonic Unleashed would be old-school Sonic gameplay--with the innovation that Sonic could now turn into a werewolf that punched things. Seriously, if somebody shoehorned in Sonic 2 game logic into a modern graphics engine, I wouldn't mind, just stop the innovation!
On the other hand, Half Life 2 Episode 2 felt pretty stale, especially compared to the rest of the Orange Box. Episode 1 was exciting because Alyx Vance felt chillingly like a real person, so I didn't mind playing what was basically more HL2 levels. However, the innovations in Episode 2 were mostly graphics and animation related, the one gameplay change (the "strider buster") was too minor and came too late in the game to make the game feel fresh.
If a publisher asked its customers whether it wanted innovation or just rehashing in several upcoming titles, they'd find that the answer really depends on the title.