I think I would have said Thief Gold by a SLIGHT margin back in the day, but overtime I think Thief II has probably stood out as the better game by an equally slight margin, if only for having more thematic focus. I heard also that the music and atmosphère of Thief: Gold and Thief II were incredible.
The 2014 one, is good in a technical pov but lost some of it’s atmosphere. Why did you even include the 2014 reboot? Not even worth pirating. Thief 1 had the better story. Gameplay is generally good, though it can be inconsistent. Final couple of levels are kinda trash, and the Gold levels are a bit too large. Thief 2 had the weaker story. Gameplay is more consistent. Some levels like Trace the Courier and Casing the Joint are supremely underwhelming, though. The only levels that took me well over 2 hours on my first attempt were Thieves Guild from TG and Sabotage at Soulforge from T2. Both levels are huge, with Thieves Guild being a bit too obtuse with its objectives, and Soulforge simply has a LOT to do.
I mean they’re great games, but I mean, the levels are fucking huge. Its just arduous and you get turned around or you get just plain lost. This was the biggest hurdle for me. Sure its all about experimenting your way into whatever method works best to complete objectives, but I straight up stopped playing when I got to the mine/ crypt which is what- the second mission? The third? The game takes literally an hour or two to clear most levels and that’s counting any hidden treasure or optional stuff to find.