Still holds up.
As far as action movies go, I honestly don't know any in the genre that manage to surpass T2 both in terms of action scenes and in actual narrative. It's where the Terminator series hit it's peak, and they really should have stopped making movies after it.
I really should't have to explain the plot- who doesn't know the premise of Terminator at this point? Super advanced death robot disguised as a human comes back in time to kill John Conner, the leader of the resistance and the only thing hindering the advanced AI of Skynet. A simple set-up, though this time it leads to some very interesting moments such as an encounter with the individual who would help create the Terminator's, Sarah Connor's mental state and becoming what she despises the most, and the idea of a Terminator coming to understand the concept of humanity.
The special effects are still phenomenal, even moreso when you realise the movie is more than twenty years old. The T-1000 is just a marvel to watch, and every time you see that liquid metal monster in action you'll be amazed at the spectacle. And of course the other action scenes are top notch- from the truck chase, to Sarah's nuclear dream to the final battle at the steel mill. They all make for great spectacles that, to me at least, surpass the kind of action scenes you'll find in modern movies.
The acting is also quite exquisite- Hamilton and Furlong put in great performances as the mother and son, and Robert Patrick manages to make for a very intimidating Terminator in his own right. Even Arnold puts in a surprisingly good performance, both using his usual imposing stature and build that made for such a fearsome figure in the original movie, but also adding in the idea of his Terminator taking on human aspects with surprising effectiveness. Despite his reputation, it's a very good performance.
In conclusion: a must-watch.