There's a lot of talk about Beyerdynamic, Sennheiser, Grado, AKG...
But I don't see Fostex mentioned that often? How come? Are they not good?
Maybe you mean stock Fostex; since 2010, modded Fostex (e.g., LFF, Mr. Speakers, Thunderpants, ZMF) have become relatively popular. Few listeners have tried stock Fostex. I have a high opinion of them. I brought a pair to a meet and several members wanted to try them because they'd never (!) heard stock. But modding really changes / improves them, and the self-modding community here is so encouraging and helpful (http://www.head-fi.org/t/618659/fostex-t50rp-incremental-mods-and-measurements).
I always forget that "Fostex" generally means two very different sorts of headphones (T50RP and TH900). TH900 is well-loved and will become popular among the astronomical spenders. It's an exciting dynamic headphone and it's very comfortable, similar to Denon AH-Dx000.
Fostex made the drivers for the old Denon models. Denon dropped them for some reason, so now Fostex makes the THx00 models that are similar to the old Denons and very popular among some people. Between the fact that these are only 2 models and that both are expensive, they don't get talked about as often. There is also the T50RP, but it seems like everyone either buys a modded version or mods the stock version themselves.
You probably found this too: http://www.head-fi.org/t/661955/fostex-th900-vs-senn-hd800. Indirectly related: http://www.head-fi.org/t/682652/please-help-should-i-get-lcd3-with-hd800-or-lcd3-with-th900. I haven't yet found direct T1 vs. TH900 comparisons.