I think that Semmy would have been a good fighter in the 90's but its hard to say. One thing that I always notice about Sem is that his skills are not up to par with many other fighters but his size makes up for it.
My personal opinion is that if he fought guys like Aerts, Hoost, Hug and JLB when they were in thier primes, his skills would not have been good enough to beat them. He had the luxury of stepping on the scene when all the bad boys were on the decline. I say this is a luxury because while these greats were/are on the decline he was still able to fight them and collect wins over them. To me though the wins that he has over Hoost/Aerts/JLB aren't pure wins.
Credit to Toxic for the sick sig!