Well, I agree that there's always been a lot of hype about Tezuka. I'm not a big fan of people building stuff up, but I try to ignore it. And at times it seems that some people who proclaim Tezuka as the greatest haven't even read that much of his work.
But I think Phoenix is good, although so far I've only read the first few volumes (still need to get the others). Still, I became hooked on it, and overall it's probably my favorite series so far. I think volume 4 (Karma) would be a nice one for people who are interested to check out, since each volume can stand alone.
Of course, some of his work isn't as strong. His earlier works like Metropolis don't hold up as well today (although I liked the recent animated movie of Metropolis a lot). Also, Astro Boy varies. Some of the stories are really nice, while you could tell he wasn't really trying as much in others.
Edit: Well, actually there is one series that might take the place of Phoenix. I've only read the first two volumes (3 isn't out in the U.S. yet), but I really like Koike and Kojima's Path of the Assassin/Hanzo no Mon. I haven't read Lone Wolf and Cub or Samurai Executioner, but I'm going to have to check them out too.