Unfortunately, reliability and image quality are (almost) mutually exclusive in this group.
For IQ it's the Contax G, hands down. And they are generally very reliable. I've owned maybe 8-10 bodies over the years, only one that I came across ever needed service.
But as we enter 2015, who knows how much longer these cameras will be serviceable or how long parts will be available? The original promise was 10 years from the date Contax shut down (2005.) And it does take some patience to learn what the AF system likes...
Leica R4 --- run away. The least reliable of the lot...stay away from anything earlier than R5 🙂 (this is from experience running the used dept at a camera store. We'd take them on trade, they would appear to work, and then flake out later and we'd lose $$ on them.)
Nikon F3: *very* reliable, easily repairable, and the 28 is great. The 50, not so much. Maybe go with a 50/1.4 Planar instead? That said, the F2 is *more* reliable, or how about an FM2n or FM3a?
Contax: excellent lenses, but perhaps choose a different body (I've owned the RX, ST, and Aria. If it were me, I'd go Aria...matrix metering, very light, great big viewfinder, and it is the most recent.)