Not sure if you played 3, but IMHO New Vegas blows fallout 3 away. Iron sights made the difference, the dice roll aiming thing in 3 was very out of place. Furthermore, the story is much more fallout than 3. The DLC for 3 was overall more impressive but I enjoyed it all never the less.
EDIT: I also enjoyed the hardcore mode a lot, gave a purpose to all those useless food items you found about the place, and food actually heals you for decent amounts.