I'd probably give it to Tenkaichi 3. RB2 easily had a far better fighting system and obviously, far better graphics and cel shading (I'd even say the best cel shading and character models in a DB Game until FighterZ), though Tenkaichi 3 takes the win ever so slightly due to the sheer amount of content within it due to the character roster. Not all the characters are good to use and some play very similarly to each other, but treating it as a DB simulator with a vast array of potential versus battles, it performs in that area of variety better than any other DB game. The story mode, whilst pretty lacking and uneven with what battles made the cut, at least had some structure as well as some entertainment with the What-If scenarios that could be performed in some stages (Mr. Satan beating Cell, Manly GAINZ Roshi beating
, Pan beating Baby, etc.), whilst RB2's Galaxy Mode was just a series of random battles with only a few stages linking to any kind of story.
In terms of additional modes, the roster made BT3's far more enjoyable due to the character matchups, interesting tournament system, Ultimate Battle's scenarios being pretty nice ideas and Sim Dragon being RNG done right (as well as the comedic brilliance in seeing Chichi tell your character to do their homework, even if you're SS4 Gogeta, Yi Xing Long or another top tier). There was also the ability to play either an updated version of the Ultimate Battle from BT1 or some of the highlights of the courses from BT2 via disc fusion.
Raging Blast 2 had....a repetitive series of battles with Battle Zone (with a ridiculous difficulty spike with the final Zone and all the Ultimate Zones) and a tournament mode that would only unlock a few pictures and announcer voices, which isn't just a step down from what BT3 would give you, but a complete step down from the previous Raging Blast game.
As far as other minor things, Raging Blast 2 at least has a far better soundtrack. Whichever Dragon you got from gathering the Dragon Balls was at least less RNG based, usually following a pattern of Porunga appearing after summoning Shenron 2-3 times, and the items (whilst far harder to unlock 100% due to the difficulty of the Ultimate Z ones) were at least far better when it comes to cosmetic things such as the Halo or removing scouters). The way battle damage is utilised in RB2 is also better due to being the same as in BT1 and 2 to help give the feeling you were wearing down your opponent, rather than it only coming from being hit by a select few Ultimates or losing a beam struggle like in BT3, regardless of how much health they still had. The battle damaged costumes in BT3 were far cooler though due to more than a few of them showing more than just a few marks.
Nevertheless, BT3 gets the win in most of the areas that count for me to say it's the superior game.