i am going to by a game later, but stuck between Mass effect, call of duty 4, quake what is the best for just single player!

I go with Call of Duty 4 because

The GOOD
*High-quality story mode packs in a lot of thrilling and unexpected moments
* Well-designed multiplayer progression gives you something to shoot for online
* Terrific audiovisual presentation.
*Terrific graphic.
*Outstanding gameplay

The BAD
*Caimpaign mode is much shorter than those of the average shooter.

Depends on what you like.

I would choose between call of duty and mass effect.

Call of duty is an amazing game and on verteren difficulty should make the game last.

Mass effect is like oblivion and the will last you longer in terms of single player but can get boring and there isnt much action.

If your on xbox live, call of duty is the game to go for.

I would go with Call of Duty 4.