I think the magic system from 4th was maybe the best of all (i started at the beginning of 4th about11-12yrs old ). Also you could have any monsters you wanted as mounts. I had a goblin riding cockatrice after that 10k battle report in white dwarf. Goblins could have great weapons too! After they cut all that out and tightened everything up giving much less diversity.
However i think 3rd edition has so many cool things about it (i never got to play it) i reckon it was the most magical time gw had. So much character in the rules and the models (RoR). My 1st ever visit to a gw store still had plenty of these models in (orc dog carts- been fixated on them ever since).
The 3rd ed rule book is awesome and i recently discovered it advises black lines to break up the colours (which i do). Im about 33 years behind the times!
The triangle formation for infantry sounds cool.
3rd ed is the edition i wish i had played the most, but it did have some faults, cannons too strong and lengthy movement phases.