Like what, having the same control scheme and character customizer?
More so the very gameplay in general. It was an overhead camera thing until Fallout 3, and it probably did save the series. After Fallout 2 it met nothing but shitty troubles.
And I believe I've mentioned before that the gameplay of Fallout 3 isn't what makes me dislike it. In fact, I felt like it was a good modernization for the series. The combat felt really simple, but NV did bring more depth into that.