The original
"Law & Order" is the best, a great show and it still has legs - though my favorite cast by far was Chris Noth & Jerry Orbach/Sam Waterston & Jill Hennessy. I haven't liked any of the female ADAs since Cary Lowell left, and Stephen Hill was a huge if subtle part of the show's soul, so he's greatly missed now too. Even with all the defections and additions over the years and it not being the powerhouse it once was, it's still a show watch.
"Law & Order: Special Victims Unit" is routinely average to lousy. It's not really the fault of the cast, which is pretty solid (especially Dan Florek reprising his role from the first years of the original, and Richard Belzer reprising his John Munch from
"Homicide: Life on the Street"), but the stories and the format are extremely weak. It's mildly watchable, but a huge disappointment and shouldn't even bare the
"Law & Order" name.
"Law & Order: Criminal Intent" on the other hand is a very fine show. The cast is amazing, not just D'Onofrio - though he is clearly the star, but also Erbe, Sheridan and Courtney B. Vance. The scripts are well constructed, and it has different angles and tones than the original
"L&O". It's a darn good show, if not up to the genius of the original. I don't usually watch it on Sunday nights - especially when it was up against
"The Sopranos", but I most often catch it on USA on Fridays. They're really built more like
"Columbo"s, where the guest star killer is identified for the audience right up front, then it's the cat and mouse game of watching D'Onofrio's Detective Goren figure it out and make them squirm.