Yes, Ebert was the only critic who could tell you how to improve as a film maker. His integrity was incorruptible. He knew things about film that none of the critics around today seem to know: a complete knowledge of films of the past, what it takes to make a film since he did one himself in the 60s, and how to make a film better. He will be terribly missed.

He comes from an old school of critics. There are plenty other good ones today, they're just not as fortunate with the media exposure Ebert got.

Some of my favorites are Glenn Kenny, David Bordwell, Jonathan Rosenbaum, Kent Jones, and others I'm missing.

Agreed with the mention of Jonathan Rosenbaum, the best critic I've read yet (but then again I am not familiar with the works of the others you mention).

Not a replacement, but my favorite movie reviewer is Anthony Lane (New Yorker).

Yes, both Anthony Lane and David Denby are quite good (though very different in style from Ebert).

A.O. Scott

Mark Kermode from the BBC? Granted you mostly have to listen instead of read, as he's primarily a radio reviewer, but he's damned good. And obstinately opinionated, which makes for some fun review rants.

Check out his "Sex and the City 2: The Movie". Legendary among his fans.