Harder to think of voice acting that really makes a game for me, but I would say that the Portal series would fall into that category.  The brilliant comedic voice acting elevates a fun puzzle game into something magical.

Breaking a game is easier to come up with, last example would be Arc Rise Fantasia.

realy KZ2!

i think it was KZ3? the HG voices seemed off. amd most of the othere were weak?

"Have you heard, apparently the Wilder brothers are squabbling with Stuart again"

The dialogue and voice acting are terrible in TDU2, it was funny at first, but not after hearing that line every other race. "I wooonder WHO will WIN thee RACE" ugh.

The characters and car handling aren't much better, so at least its consistent lol. Oh well, it's still fun to drive around Ibiza and Hawaii. I wish GTA would have gone that size after San Andreas.

I started a thread about this particular game that really got to me with one of the reasons being what I thought to be the terrible english voice acting (Although I didn't mind the main characters). And I did upset a lot of people for saying it. The game....

Metal Gear Solid 4.

What you're not understanding is Portal was done with the western audience in mind.  Few people here are complaining about western made games with voice acting (aside from perhaps that guy who said Kratos, which I kind of agree).  But Portal never suffered from being relocalized and dubbed with a much smaller budget.  In fact, Portal, like something such as Assassins Creed or any Bioware game, got major well known voice actors and put entensive focus on the voices.

The major problem with voices in video games are when you start to look at the Japanese made games which come over to the west.  That's when you get the legendarily bad voices like in Sonic, Final Fantasy and Xenosaga.  Because they're redubs with emphasis put on how fast and cheap they can redub the voices.

I usually NEVER care about voice acting or not.....

...but Trauma Center: New Blood was WAY better than Trauma Center: Second Opinion, and one of the major fqctors was the voice acting being present in New Blood.

not me

The lack of Kevin Sorbo will ruin this game.

House if the Dead 2's voice acting is so bad that it made it my favorite light gun game ever. 

HA! So true! "Suffer like G did!"

That reminded me of another good voice acting game.

House of the Dead Overkill is certainly a mediocre game if not for the outrageous script and voice acting. One of a few game I recomend  to people just for the VA and F-bombs.