So are you talking specific player movement, the feel of speed compared to the surroundings or just the overall pace of the game?
I'm talking about player movement speed and the maximum speed at which any given player can move.
You can have the fastest characters ever, but if it's on a massive outdoor environment, it's not going to feel fast.
Which is a testament to Tribes' speed. Huge maps and I still feel like I'm moving really fast.
The only character in Tribes that was fast was the Light or no armor/loadout and they weren't that fast unless you got airborne and started skiing. Medium and Heavy armor loadouts were not fast at all.
Skiing/flying in Tribes is equivalent to running and jumping in any other shooter. It's the primary means of moving around the map and it's faster than the movement in any other game. While it's true that medium and heavy have slower default acceleration than light armor, it is possible to move very quickly in them if you have enough skill. Check out the Youtube movie I linked for examples.
Tribes also had indoor environments that you could not Ski in to gain speed. The gameplay indoors was significantly slower than that of Quake or Painkiller.
This is true. If you remove skiing from the equation, Quake and Painkiller are faster. However, removing skiing from Tribes is like removing bunny-hopping from Quake and Painkiller.
So no, Tribes is not what I would call a "fast" game, certainly not the "fastest ever".
In the context of fastest possible player movement, Tribes is the fastest ever.