Personally...I'd rank them like this.
- Tekken 5/Tekken 5: DRO (brought the series back to it's roots, top notch graphics, amazing music, the gameplay entered a new peak, fan favs returns and with DRO there's online, just amazing all around)
- Tekken 2/Tekken 3 (these games had everything and they're the games that introduced people to Tekken. dope music, basically when you think of Tekken, it's these games)
- Tekken 7 (amazing, dope and it also started the "seasons" for Tekken titles, gameplay-wise it has the best gameplay out there)
- Tekken 6 (cool game but it didn't really push the bar like the previous titles did)
- Tekken 4 (aesthetics, music, vibe, walls, pretty experimental)
- Tekken (the first one, the others could only improve the format)
Skipped tag since I didn't play em much. I'm also looking at everything when I say this. That 5/DR0 era might be arguably my favorite Tekken era.