Uhhh what? The BttF sequels were awful in comparison to the first one. Don't get me wrong, they are still enjoyable, but don't compare to the first.
Also, are we talking whole anthologies into account or just talking about the first and the sequel? Because Alien and Aliens were both REALLY good. Obviously Godfather Part 1 and 2 - as they are both known as being some of the greatest movies ever made. Some more...
T1 and T2.
Bourne Trilogy was good.
Leathal Weapon 1 and 2 were awesome.
The Raid and The Raid 2 were great action flicks.
Mission Impossibles have gotten better as they have gone on (only bad one was #2).
The Nolan Batman movies were really good.
I haven't seen Blade Runner 2049 (though I own it) yet, but I hear it is really good.