It's okay. Not as good as the two others, but not awful either. yes, I happened to like Chronicles a lot - I liked the design and mythos of the necromongers - they felt like something out of a Franco-Belgian comic. No major spoilers here, but the comments are anything-goes, so be warned.
The best part of the movie is the first 30 minutes, with a wounded Riddick alone versus nasty beasties. I liked the design of the beasties, especially Riddick's thylacine-like companion seen in the trailer.
But as soon as other characters arrives, in turns into a poor man rehash of Pitch Black - the secondary characters are nowhere as interesting as Pitch Black of even Chronicles' characters. Katee Sackhoff's character is especially disapointing - she was hyped up as a kick ass mercenary, and instead she's a barely developed sidekick with a very confusing sexual orientation (so, she's a lesbian, but wants to have sex with Riddick? I think?) and their is also a little something that irked me about her character, but it's pretty spoilery so I'll only talk about it in comments if asked. Oh, and there is a lot of gratuitous boobs in this movie, for some reason.
So yeah, is Riddick a good movie? Yeah. Is it a great movie, or will I watch it as much as I watched the two others? Nah. Should you see it in theaters? Not really - you can just wait for the BR and watch Pitch Black again in the meantime.