Series die or degrade, that's just part of life. Worms killed itself on the PC, as did the X-Wing series, Krondor series, Heroes of Might and Magic, and more. Even good series like Jedi Knight ends eventually. Yes, some series die when they go multiplatform, but I think that's more about them getting gready and losing focus on the gamers than it is about going to two platforms. There are a lot of good series that degraded on its own without consoles' help. The rate does seem to be higher on multiplatform series, though.

But I don't think GTA or C&C3 died from going multiplatform, quite the reverse. And certainly going multiplatform has increased the budgets of many developers, meaning we get better graphics quicker than we would otherwise.

Betrayal at Krondor
Deus Ex
oddly enough, I'd vote for Tie Fighter too, very immersive.
Any Bioware game also counts high on the list of course