SDBZ is more of a “proper” fighting game than the other DBZ games. It’s based on the manga rather than the anime and has a great levelling up system that’s somewhat like the skill tree in Diablo 2. You feel more like you’re actually fighting than just triggering off cut-scenes, like in the other DBZ games. It’s quite restrictive compared to the other ones in the sense that you have comparatively limited ki and can only fly for a short amount of time (in Tenkaichi you can fly forever.)
Tenkaichi is good because the camera is behind the fighter and the arenas are pretty vast. It actually does feel like you’re in the anime, chasing Buu around the city or flying around the islands where Vegeta nearly killed Cell. The landscape damage is impressive, all buildings can be destroyed and you can turn the Cell Games arena into a huge crater! The fighters also have visible damage, like cuts, bruises and torn clothes.
In short, SDBZ is a more tight and better designed game than Budokai or Tenkaichi, It’s still nowhere near being a 3rd Strike level game, but it’s still the most accomplished in that sense (afterall, designed by one of the SF2 team). It doesn’t have that many characters, but those it does have all play relatively differently and can turn out even more differently depending on how you level them up - you can even learn other characters moves so you could have Videl doing Destructo Disk or something. You can also do things like change Trunks’ sword for a longer one, or a shorter but more powerful one… As well as gaining “passive” skills, like ki recharge or the ability to fly at someone without being knocked out of it (still taking damage though).
Tenkaichi is almost like a DBZ fight simulator, with an over-the-shoulder 3rd person view and huge arenas to fight in, as well as impressive damage modelling on everything, as I said before. By far the worst thing about it is that while the basic fighting system has a lot of options (it needs - and has - a tutorial in-game) people only have a few supers and specials, and many of them are shared between the enormous cast of fighters. It almost has every character to have appeared, as well, and all of their forms. While SDBZ feels like a 2D fighter forced rather uncomfortably into 3D, Tenkaichi flourishes in 3D and is clearly entirely based around it.
Budokai is somewhere in between. You can have more traditional fights (like in SDBZ) but still not that traditional, but it also feels like a celebration of the sheer destruction of the DBZ fights and the variety of characters, which is something SDBZ falters on.
To be honest, I have never really been that impressed by Budokai. SDBZ is a step in the right direction at making a true fighting game of DBZ, but still has a long way to go. Tenkaichi has a lot of options, a lot of scope for different strategies and is quite freeform but is much more like a DBZ playset than an actual fighting game.