I was lucky enough to play the original games when they came out, and I still love Fallout and Fallout 2 and play them from time to time, own them in hard copies and also in digital from GOG.com, bought them before GOG.com had to stop selling the Fallout games.
For me Fallout 3 is quite an interesting game, I like it and really enjoy the ruins of the Capital Wasteland, explore the metro areas and abandoned factories and offices. Fallout 3 wins at the map/world setting, but Fallout New Vegas wins at the game features and overall game improvements, also the ability of being able to join three different factions to beat the game or go wild and make your own is also a plus, Fallout 3 unfortunately had no side to choose from, couldn't join the Enclave, always had to fight them.
But to be honest and the main reason I just registered to post on this thread and participate in this poll is because I didn't see anyone mention a great project that integrates Fallout 3 and all of it's DLC's into Fallout New Vegas called Tale for Two Wastelands (or TTW for short). Unfortunately it is a mod so it only works with the PC version of the games and to install it requires an installed version of Fallout 3 and all of it's DLC's and also Fallout New Vegas with all of the DLC's installed (with the exception for the stuff packs or Courier's Pack, those are optional) and it does what I just said, you can play Fallout 3 and all of the DLC's using the Fallout New Vegas engine and features, the team there made a train station (using actual blueprints for the 1940's real train stations that actually existed in the real world) that requires a short quest to activate, after that just buy a train ticket and ride to New Vegas and play there, after that one can go back and forward using that train and buying new tickets, companions can follow the player from each of the wastelands to the other, items from New Vegas were integrated into the Capital Wasteland, so you can find doctor bags and Hydra, etc in the world and on vendors, iron sights for fallout 3 weapons, armors updated to be like in New Vegas, etc.
I really advise anyone that has both games to at least try this mod, you get all the setting from Fallout 3 and all the features and improvements from Fallout New Vegas, and it even makes Fallout 3 work better and with less crashes than just play Fallout 3 by itself.
The community is also quite friendly and helpful in case people have problems installing the mod or trying to play with added mods (both Fallout 3 and Fallout NV mods work, but the Fallout 3 ones need to be converted).
To find a Tale of Two Wastelands just google it, since the Nexus doesn't allow it to be hosted there in case Bethesda would get angry for some reason by the project.