I like my guns to be capable of 1 inch 3 shot groups at 100 yards. I can live with 2.5 inches if that is all I can get. I'm talking about off from a bench in good weather though, not off hand.
If I have a gun that will not group better than 3 inches after experimenting with different loads I will not be owning it very long.
Something to consider is that you need to be able to shoot that well in the first place. I hear many people complain about a gun not being accurate and it ends up not being the gun. Some don't take the time to find ammo the gun likes or just don't shoot that well to begin with. If you can't shoot one inch groups or better don't expect your rifle to.
In all honestly if I could shoot 5 inch groups at 100 yards off hand I would be happy. I just don't shoot that well off hand. However I don't do it very often, even when hunting I normally have something to rest the gun on.
Paul