Many years ago I had a lamb kebab (Greek, I think) on one of the corners of Fifth Ave opposite the Plaza Hotel. A street food vendor with his cart near a long-established shop selling amber sold the most delicious, tender kebab I have ever eaten. (And I don't normally like lamb!) I am sure he is long retired, but perhaps an old-time Manhattanite might know about him or someone else as good as. Certainly his kebab was better than anything I have had in any up- or down-market restaurant!

My limited experiences with those carts is that it's hard to know if you're going to get one of the kebobs that he did a couple of hours earlier and has been continuing to keep hot and is now dried out, or if you're going to get a really nice fresh one. Someone told me you almost need to be a regular at a cart to get good value and the best quality from a guy who knows you.

Try the vendy awards site.

http://streetvendor.netfirms.com/public_html/

I've never gotten sick from NYC street vendor food, but I guess I'm lucky. Lost count of the times I've gotten sick from restaurant food.

Anyways, you can tell the good ones if there's a long line of "corporate working stiffs". Some vendors serve up food that is way better than your average restaurant TGIF/Ruby Tues/Olive Garden/McDonald's with a liquor license fare.

I don't know about the guy outside the Plaza hotel. But these days, the most popular street vendor is the "Egyptian Guy" aka "Chicken Platter guy" or just "53rd & 6th Guy".
He has a cart on the corner of 53rd street & 6th Ave and is especially crowded late at night. While there are a few other carts on that corner, this one will invariably have a long line. The NY Times has written about him.
http://www.53rdand6th.com/

Besides that one, Mamoun's Falafel, a hole in the wall falafel place, on McDougal near Bleecker street is famous & excellent. Try the lamb shawerma. Their kebabs are excellent too.

The chap on the eastern side of Fifth Avenue, between 58th and 59th Sts (which I assume is the pitch nancy is referring to), was making his kebabs fresh last weekend. Other clients were waiting while they cooked, and appeared appreciative.

Probably because his hotdogs were about as mediocre as they come.

The vendor didn't sound Greek

This website has user ratings of street food vendors.
http://www.streetgrub.com/
The guy on 53th and 6th gets 4.5/5*s.