The 6809 is a great chip, but it's a cheater. Internally it's a 16bit device.

1802 is kinda neat, if you can get used to the programming model. All those registers!!!

 

I'M TOO SEXY FOR MYSELF. Now as we have established that fact. I liked the Z80 quite well. Was it sexy...Nah not sure about that

I'd put the Z80 as 2nd. Both the 6502 and Z80 are still alive in some form.

The others mentioned don't have the simple elegance these processors had, and were easy enough to program that anybody can pick it up fairly easily, depending on which incarnation of uP you are working with.

You don't need 16 or 32 bits for many common tasks, though I remember times I wished for 9 bits.

 

I would agree that the 6500/6800 series processors are the easiest to learn to program. MANY moons ago I purchased an AIM65 development system by Rockwell that was 6502 based. Having watched others in my environment pray over long lists of code while drinking much coffee and filling lots of ash trays. It just didn't look like fun. I took a consulting task that called for a device that could sing, dance and do dishes. The AIM system appeared to be a good value and offered very good human interfaces in the form of self contained keyboard, display and printer. I bought one and jumped in.

After less than a month, I was writing code I could demonstrate and sell. I pondered why I took so long to broaden my horizons. Then I looked at all the other 'low cost' development systems an the architectures of their host/target processors. No way I could have progressed so quickly with any other offering.

If I were tasked to teach and demonstrate processors, folks would be hard pressed to talk me into any other architecture for helping folks get their feet wet in the byte pool.

 

Ha! I've got an AIM65 sitting on my bench! It kinda works -- I need to dig out the power supply and replace the 5V-only supply I checked it with. Unfortunately, my 6809 Dev board had "mental problems" two weeks ago, so it's consigned to the "I'm gonna fix this some day" pile.

--Rich