Playing Tekken Tag again in HD is really awesome, You really forget how incredible a PS2 game that was. First thing I tried was Tekken Bowl - Awesome fun. Randomly enough I bowled over Doctor B who stands as a spectator and got a trophy for it...
I think Tekken Tag is most likley the last really great Tekken game that came out. Although I like the others (Yes, Including no 4

) this tekken most probably got the most gameplay time from me and has the best soundtrack too!
The Tekken Tag Tournament 2 Prologue is a preview demo of the upcoming TTT2 and kinda ties into the Tekken blood vengeance movie with the selection of characters you get to play with. Very nice demo for them to include, it uses a modified version of the Tekken 6 engine but plays just as well as Tekken tag (including some remixed songs from TTT1) with full 3D Support.
Tekken Blood Vengeance, Although targeted for Tekken Fans it was written for non gamers too. Will post a review in the Blood Vengeance thread shortly. Just so you know, Its Written/ Directed by Dai Sato (involved in Samurai Champloo, Cowboy Bebop, GITS SAC).
I highly recommend Tekken Hybrid for guys that want to relive some great tekken gaming, preview the next game and get a pretty cool CG movie to watch. Both games have full Playstation Trophy Support and make a great addition to a fighting game fan's collection!