L>P>M released loads of these as boxsets (all 4 piece)
i have the garage, acid, underground, rave, hip hop, jungle and acid boxsets.
most of the boxes are poor with only one or two good tracks
jungle is pretty good with recogniseable (now old skool)trax
the rave box is worth the asking price as has loads of classics (playing with knives, prodigy, 4hero etc)
usually you can find these boxes in bargin bins at large record stores
have also seen techno boxset, drum and bass (96) and happy hardcore

I tend to disagree with the above poster. IMHO the producers of these box sets really went out of their way to pick some (mostly) obscure tracks that never made it onto CD or anywhere else, the sort of tracks that have been collecting dust in someone's record collection.

I have a special liking for this jungle collection because it perfectly captures the "missing link" d'n'b that was just starting to morph into more "modern" jungle versus old school rave tracks.

The Best of Acid series is only for people who really, REALLY, like the 303 (and unfortunately, was stolen when during a smash 'n grab here).

The Best of Hardcore series is highly recommended. Almost all of the tracks are highly obscure, and many are much more "techno".

I can't speak for the Garage or Underground ones, but any completist is advised to pick these up. If you're looking for just a "Big Choonz Of [Whatever] Era!' sort of comp though, yeah, you'd be better off looking elsewhere. Just my $.02...