I agree with Boonstak; 90s and 60s were the best eras for rock.
The 00s are pretty good too though.
Bands like White Stripes and The Killers put out excellent stuff IMO.
Also, today, there is a resurgence of 90s acts like Green Day, Red Hot Chili Peppers, and Smashing Pumpkins, putting out some of their best stuff ever.