Revell Germany sets the standard. I've just bought the new set of two Hummers, and the level of detail has to be seen to be believed. Also, they've got a 1/72 FAMO, with link & length tracks, on the way! Bear in mind that some of their stuff is ex-Matchbox, but still OK by mid-1970s standards, and sometimes unique subjects.
Italeri come second. Nearly all their stuff is ex-ESCI, but that's usually no bad thing. for every turkey (Tiger II), there are two stars (Sherman, Valentine). However, there's a new mould DUKW on the way.
Mirage produce a number of astonishingly good early WW2, mostly Polish stuff, spoilt only by their rubber band tracks (though aftermarket PE tracks are available).
Eastern Express, Alan, Omega K and Roden produce an useful range of stuff from the Great Patriotic and Cold Wars and their approach to modelling the T-35/ 85 is an interesting contrast to the Revell Germany one.
JB Models produce an interesting, well-detailed and accurate range of British wheeled and softskin stuff, and a Vickers 6-ton tank.
Dragon, based on die-cast toys, are embarrasing, and I can't think of anything they do which Revell don't.
The Heller/ Airfix Deuce-and-a half is pretty good, but needs some work with details.
Most of the rest needs to be approached with caution, but often they are the only gane in town. There are a lot of useful reviews and other stuff here:
www.ontheway.us
Hope this helps,
Chris.
Cute and cuddly, boys, cute and cuddly!