I'm surprised to see that Hackmaster, which began as largely a copy of First Edition AD&D, is not mentioned. I haven't followed its development, but there is certainly a great mass of Hackmaster material in print (even a version of SpellJammer).
I've not followed the "revival", but if I could characterize the difference between old school D&D and Third Edition, it was that it was much simpler, and much more based in cooperation. D&D 3 is, as someone said "fantasy Squad Leader", with every character designed to allow it to be independent, a "power gamer's fantasy".
4th edition, though it may be a good game and certainly emphasizes cooperation, isn't D&D.