I definitely recommend 1 and 2 if you find the time because they're wonderful.
As an introduction (since you're looking at this because of 4s announcement) I'd say go with FO3 or NV. New Vegas is similar to 3 with a lot of gameplay improvements while I've always felt 3 had a better atmosphere to NV. There are references to past games but you don't need to know what's gone on elsewhere to understand what's going on there. They are, as someone else pointed out, probably closer to how 4 will play.
[youtube]S0ximxe4XtU[/youtube]
Edit: New Vegas' DLC is pretty great. Old World Blues had me laughing the entire way through.
As an introduction (since you're looking at this because of 4s announcement) I'd say go with FO3 or NV. New Vegas is similar to 3 with a lot of gameplay improvements while I've always felt 3 had a better atmosphere to NV. There are references to past games but you don't need to know what's gone on elsewhere to understand what's going on there. They are, as someone else pointed out, probably closer to how 4 will play.
[youtube]S0ximxe4XtU[/youtube]
Edit: New Vegas' DLC is pretty great. Old World Blues had me laughing the entire way through.
