Depends on what you consider classic. I like a little AC/DC, Midnight Oil, Men At Work, Silverchair, and please don't pelt me with rotten eggs for this but early Olivia Newton-John.
The first one that came to mind is the Grateful Dead just now, but I wasn't really trying hard to think, compare, or contrast. But I do like the Grateful Dead. I have an appreciation of Yes, but I wouldn't say they are my favorite either. If I had to identify favorites, and I could only pick one, I think I'd go with the Beatles. I just really like their ethos, and find that so many of their songs leave me feeling happy or with good vibes. I think that's important, so yeah.. them.