If you loved F1 and F2 do yourself a favor and skip F3. In the essence, New Vegas captures the spirit of true Fallout, Fallout 3 doesn't even try.
I played F1 and F2 when I was a kid and loved both. I loved FO3. I would never advise anyone who liked the originals to skip it. New Vegas had better writing/quests/items, but Fallout 3 had, in my opinion, vastly superior world design.