I don't really wring my hands too much about what system I use for gaming. If you have good players, you can have a great time with any edition of D&D. If I lost all my 3e books tomorrow, I'd be just as happy to drag out my 1e books and use those instead. That having been said, I moderately prefer the current edition of D&D for the following reasons:
-- the core mechanic is applied consistently across the rules, so that rolling higher is always better
-- conditions like "stunned", "invisible", and so forth are much better codified than in previous versions
-- ability scores seem to matter more, and have been tied more closely and consistently with saving throws, combat bonuses, and so on
-- some quirks from earlier editions have been hunted down and shot, and replaced with better solutions. I'm thinking saves, multiclassing, XP, I could probably come up with more examples.
But there is still progress to be made:
-- NPCs and monsters take way too long to create, and are hard to do on the fly compared to previous editions.
-- skill-point management seems to take an inordinate amount of time. I'd like to see skills simplified greatly.
-- combat seems to steer you towards miniatures-based, grid-based play, rather than descriptive play. Nothing against minis, but I like fast combats that take place in the shared imaginations of the players rather than on the table.