Well, Cataclysm was developed by a different company than HW, so of course it wasn't that similar to HW.
I think HW2 made a good sequal. They changed a number of things in it. You expect a sequal to be like the original, and that's how HW2 is.. and even better IMO.
As for the learning curve, I thought HW had a bigger learning curve than HW2. I remember the 2nd level in particular.. that was difficult for such an early mission. I suppose HW2 wasn't as hard for me since I had already played HW not long before it.
Tron2.0 for GOTY? Hmm, we'll see about that.
This space is available for rent