I was reading the thread about Ryun possibly being the best miler of all time and his WR run on cinders. I was fortunate to have grown up in Mississippi where, believe it or not, there are still lots of high school tracks that are cinders. I remember running the mile at one track meet my high school senior year and running 4:52 on a cinder track. I felt like I was slipping with each step and couldn't really get a full stride. The very next week, we had a home meet (rubberized track) and I ran 4:28. I ran slightly harder at the home meet, but let me tell you...there was a world of difference on the cinders versus the high-tech track.
No doubt in my mind Ryun could have DEFINITELY run 3:20-something for the 1500 with today's high tech tracks, apparel, wind-blocking stadiums, rabbits, European atmosphere, nutritional supplements (not drugs either), and financial assistance that present-day athletes have.
I know there have been tons of threads on this, but I say top four 1500 guys of all time:
El Guerrouji
Ryun
Morceli
Lagat
With no particular orer.