Is 2 2 2 4 good for 100 amp service?

Yes, 2-2-2-4 aluminum is good for a 100 amp dwelling service or main feeder. NEC Table 310.12 permits number 2 aluminum for 100 amps where the conductors serve the whole dwelling, and the number 4 is the equipment ground.

That 310.12 allowance is the 83 percent rule for dwelling services. Outside it, plain Table 310.16 rates #2 aluminum at 90 amps at 75C, which is why the same cable reads differently in different articles.

So the same 2-2-2-4 feeding a detached shop as a general feeder may only be worth 90 amps. Application decides.

Use aluminum-rated lugs and antioxidant compound at terminations, and torque to spec; those details are where aluminum feeders go wrong.

Confirm your exact case with the 100 amp wire gauge calculator, which applies 310.12 only where it legally fits.