Compiling my current ranking of Tekken games:
1. Tekken 6
+ Loved the bound mechanic
+ Fights felt very grounded and immersive with a great level of strategy and depth (mind games and wall pressure felt great)
+ Good tracks in the OST
+ Best customization the series has ever had to offer
+/- Both good and bad new character designs (Miguel, Leo, and Zafina being good and Bob, Lars, and Alisa being bad)
- Netcode
- Awful SP campaign and story
- Took 2 years to release
- No good tutorial mode
- Loading times
2. Tekken Tag Tournament 2
+ Diverse and large cast with return of classic loved characters
+ Amazing soundtrack
+ Excellent new gameplay mechanics (tag assault in particular)
+ Wonderful netcode
+ Timely release on consoles
+ Tekken Tunes
+ Record function in Practice
+/- Okay tutorial (that I started but never completed)
- Worst customization in series history
- Tag shenanigans
- No instant rematch option in vs battle
- Philippines stage
3. Tekken 5
+ Very timely console release and still feature packed
+ Enjoyable SP campaign
+ Excellent new character designs
+ Best OST in the series
+ Fun gameplay
+ Some hilarious, enjoyable endings
+ Best intro trailer in the series
- Tekken 4 art style was better and they should have stuck with it
4. Tekken 3
+ Time skip with many new well-designed characters
+ Fun gameplay (Gon, Dr. B, and True Ogre were truly fun albeit irritating characters to play against) / introduction of sidestepping for all characters
+ Excellent OST
+ Tekken Ball
+ Great cinematics + amazing graphics (for its time)
- Character balance
5. Tekken 4
+ Best art style in the series
+ Amazing graphics (for its time)
+ Excellent stages
+ Great new character designs
+ Good storytelling
+ Good OST
- Character balance
- Stage balance
6. Tekken 7 (current standing but could go up with updates + DLC)
+ Good graphics (well-detailed characters; good looking stages for the most part, except Jungle Outpost and Souq look awful; excellent new hit effects)
+ Updated defaults for most characters after a long while and did a good job with most of them (Xiaoyu and Feng have never looked better; though, Hwoarang looks dumb)
+ Good OST
- Gameplay lacks new and exciting change; is just a re-adapted Tekken 6 with focus attacks and ultras.
- Some abhorring new character designs and/or character personalities (Chloe, Gigas, Devil Kazumi, Josie)
- 2.5 years to console release
- Spotty netcode and egregious matchmaking (on PS4)
- Customization
- Lacking features that were present in arcade mode / not as feature packed as past Tekken's
7. Tekken Tag Tournament
+ Awesome OST
+ Great selection of characters
+ Fun four player fights with the PS2 multi-tap
+ Tekken Bowl
- Not really much of a visual upgrade from Tekken 3
Not Ranked: Tekken 1 and 2 (never played these when they came out and they didn't seem to have aged well)