Gen 2 may have introduced a lot of bad Pokemon, but I'm giving Tyranitar my vote for most consistently good non-super legend in the series. It makes a strong argument for being a top 5 Pokemon in literally every generation other than gen 1 only because it wasn't in that game, but it would have been top tier in gen 1 if it were. It came with a huge list of advantages right out the gate, and none of it has ever been taken away while every new generation has given it incredibly powerful new stuff so it just always has more and more going for it. Introducing a Pokemon this good offsets a lot of the fluff from gen 2.
Speaking of fluff, gen 2 also gave us Jumpluff who I think is often underrated. Sleep Powder + subseed is incredibly disruptive; it has been a source of a lot of wins for me in ranked singles, and it has been able to do basically the same thing in every gen (I don't think it got Substitute in gen 2 itself and thus it was useless, but it got sub via tutor in gen 3 and therefore every subsequent gen so it's not like this is new ground for it).
3ds FC: 2423-3327-5637 X safari: Pupitar, Boldore, Shuckle