If you're still waiting for your copy of Fallout: New Vegas to be delivered, you can spend some quality time reading through GamesRadar's three-page history of the Fallout series. The text is pretty good, but it's obvious that they scoured the web for related images with reckless abandon - as evidenced by the F1 map wallpaper created by GameBanshee's Tyson McCann years ago embedded on the first page (without credit). Anyway, an excerpt:
The original Fallout had a team of about 100, which mostly dissolved after Fallout's release. However, about a third remained to create Black Isle Studios, with Interplay remaining as the publisher. Fallout 2 was a true sequel to Fallout in the sense that it did everything the original did, but bigger and better.
FO2 accommodated more viable play styles and a larger armory than the original, cementing it as one of the best loved RPGs in the genre. The recruitable NPCs were now more robust, allowing the player to issue more complex orders in battle (i.e. equip armor, go heal, run dammit RUN!). Furthermore, the new (reputation) system complemented the original (Karma) system; making your actions in Town A known to Town B and vice versa. The developers put the reputation system to good use as well. While the original Fallout allowed the player to go Jedi good or Sith evil, FO2 allowed players to engage in more morally grey areas. Players could become a porn star, join the mafia, become a slaver (or side against them), get married (and subsequently divorced), all of which would affect the various NPCs' opinions of you throughout the game.