I've played 3.5 mostly, with a flavoring of 4E and one game of AD&D. Despite having cut my teeth on D&D through the AD&D ruleset by way of CRPGs like Baldur's Gate, the 2E game was both short-lived and miserable (though, the DM repeatedly mentioned his intent to show us how good 3.X was by comparison, so I dunno). The 4E module was fine as long as I kept in mind that it wasn't an update/replacement to 3.X, but so fundamentally different that it was effectively a different game with the same brand identity.
3.5 will always be my special friend, though, simply for the sheer number of options it presents. I can make nearly any character concept I can concieve of, with a near perfectly tailored suite of mechanical traits to fit that concept, and be completely distinct in both flavor and abilities. It suffers from some significant downsides because of this broad toolbox of options, namely the staggering dominance of a expertly-played druid, wizard or cleric compared to any other character who isn't also a wizard/cleric/druid, but nothing's perfect.