I really hope Fallout: New Vegas manages to combine the best thing about Fallout 2 & 3. Fallout 3 was mostly a step forward but there were still some things which it still failed to replicate. But since New Vegas is developed by Obsidian which consists some of the old Fallout developers I think New Vegas has potential to be the best Fallout yet.
Obsidion has yet to really prove itself as being anywhere near as good as Black Isle. They've given us one decent game brought down severely by LucasArts rushing them (KOTOR II), two bad games (vanilla NWN2 and SoZ), and one genuinely good game (MotB). A far cry from their golden years, and I fear that Bethesda intervention could just be as bad as LucasArts breathing down their necks.