Uni-the-Unicorn!
Hero
Obviously it is different for everyone, but 4e felt like D&D to us. In fact, it is the edition that brought us back to D&D after skipping 2e and 3e.I think the only edition of DnD that didn't quite feel like DnD to me was 4e. I still thought it had some great stuff but it just didn't feel right. Meanwhile, pathfinder (both editions), ACKS, all other editions, WoW d20, Conan d20, Astonishing swordsmen and sorcerers of Hyperborea, and likely a host more, all felt like DnD.