To be fair, a lot of people went and saw Avatar in September in preparation for seeing Avatar 2.Yeah, yeah, I was there. Saw it seven times in the theater in 1991. Equal in total theatrical viewings to ANH. I absolutely loved it and consider it a classic to this day. But AWOW was still better IMO.
T2 may never be forgotten by us, but it pretty much has been by society. When it was re-released in 3D a few years ago it made a dismal $562,000 it's opening weekend (and was gone shortly thereafter.) Compared to Avatar's re-release in September where it made 20 times that.
I was one of these people as I hadn't seen Avatar since... 2009. On the other hand, I watch T2 every 2-3 years. I do really like both Avatar movies, but I don't think I'll be watching them every couple of years like T2, Jaws, Aliens, TWS etc.
People are still enthusiastically buying Terminator 1 and 2 merchandise, just look at MAFEX's recent 1/12 figure range, and Present Toy's 1/6 range of T2 figures.
It could be a generation thing (I'm 43), but I just don't see the same level of take up and enthusiasm for Avatar from the equivalent generation (say people who are around 26 now).