In terms of walk up gyros, One place is pretty much the same as the next.
I beg to differ - if you're speaking in general terms (and not just specific to Halsted St.).
If I walk into a place selling gyros and observe the grillman/counterman slice the meat from the spit and toss it onto the griddle - I'm out the door as quick as you can snap your fingers. All too often now untrained staff fry the gyros meat instead of letting it cook/crisp on the spit (which, to my way of thinking - is the proper way to prepare/serve a gyros).
In addition to the gyros at The Parthenon, I'm a fan of the lamb chops which most of the times I've eaten them (probably scores) are excellent. The Parthenon is not only "bread" (as James Ward might describe things) but also a lot of "Circus" - and the combination makes for an excellent time. On the lighter side of things there - ask Victoria to read your Greek Coffee grounds for you if she's working at that hour.