Reason being I think Diablo can get repetitive. Now if you're a fan of Diablo games then this will be much less of an issue. I'm a fan but not a raving fan and I got tired halfway through my second playthrough. My OCD forces me to enter every single dungeon and clear it out. That said I am probably going to rebuy it in a few days and play through the new content.
DR3 is silly fun. I guess you could say it would be repetitive but you can search the map for all the collectibles, you can build all the weapons, builds all the car combos, go for 100% on items in your armory, go for zombie kill challenges, or you can speed run through on Nightmare mode. All around an entertaining game and I haven't even played any of the DLC.
TF is fun but I ranked it last because of your future purchases of MCC and Destiny. You'll have plenty of shooter to keep you occupied and TF has the least amount of content of the three. Granted if you are really into shooters the online should keep you well-entertained with something new everyday so its up to you. Have fun