Tekken and & Tekken 2 on Playstation, although they are *very* close to their arcade System 11 counterparts, they are not completely arcade-perfect. the character models have been tweaked to fit in the PS1's smaller RAM. the hit-impact spark & effect thingies are lower resolution, resulting in a blockier look compared to the arcade's finer particles. the floor textures in Tekken 2 are sharper in the arcade. the names of the stages in Tekken 1 are gone on PS1. the faces don't turn when you select your character in Tekken 1 on PS1. there are probably a few other very minor differences. a few improvements to the PS1 Tekken actually--there is a video monitor that shows you fighting in the statium stage.
Anyway even though PS1 Tekken & Tekken 2 are not arcade perfect they *are* close enough. In fact, many games that were much, much farther from being arcade-perfect have been idiotically called arcade-perfect. so I cannot really blame ya :)
You are most certainly right about Tekken 3 though. it was scaled down.
that said, the Playstation2 emulations of System 11 Tekken, Tekken 2 and System 12 Tekken 3 seem to be dead on exact, as far as I can tell.
now all we need is an System 258 arcade Tekken 5 emulated perfectly on Playstation3. that, or a souped up rendition, ala Tekken Tag on PS2 ^__^