I'm not really sure what 5E would look like, but I can tell you what I like from each edition as it morphed through time.
Basic D&D - the simple, innocent feel of this edition allowed for amazing stories and feats of incredible daring without being too rules heavy.
1E - it felt almost scientific and calculated in comparison to its predecessor. The system was definitely more robust and still provided a great framework to build stories on, but the psionics system was beyond dross.
2E - the rules became more refined as roleplaying gamers now had their own niche (instead of being a subset of wargamer). The system felt alive and warm, a far cry from its antiseptic predecessor. 2e provides the best story-telling framework in D&D. Easily adapted rules and the emergence of a usable skill system.
3E/3.5E - "complicated simplicity" - using a d20 +/- modifiers for all basic rolls (good idea), skill system that usually works (good idea), customizable classes (good idea), giving rules to every aspect of gaming (bad idea), allowing the bean counters to keep "more crunch less fluff" in official game worlds (bad idea), less story more rules (bad idea), raid-style MMO game play (bad idea)
4E - i won't look for an argument here (but i'll probably get one), IMHO this version of the system is the D&D equivalent to HOL. The only things I find worth it in this system is the choice of attribute to use for an ability and the concise framework to create encounters. Otherwise, the game is still following the MMO-style of play and getting a little mechanical.
5E? - probably even more rules heavy and video game like, heavy electronic-aids dependency, though I think it will break through some of the electronic walls and make its way onto platform systems. With the rise of platform communities (XBox Live, Playstation Home, etc.) and the new technology there (like the Playstation Eye), I can see the table top gaming group moving to a virtual table top (even more robust than most of the VTT software now). D&D will gain its 3rd dimension in production, with 3D models of creatures and environments, GM's will act more like MODs or Admins and be there to tell a basic story, but the system itself will be hard-coded into the console.