One of the major contributors in my decision to buy Nikon is the lens catalog. There have been very few changes in the lens mount, and there is some fine glass available.
If you are buying used nikkor lenses online, and you want to know anything about them. I suggest that you check out Photography in Malaysia. eBay is awesome for deals, but it's a good idea to check KEH for pricing before you place that bid in haste.
I've picked up a ridiculous amount of glass in the past couple of years. I have 16mm-300mm nearly covered at 2.8 or faster in primes now, and have started picking up M42 for added weirdness. As a result, I generally carry around a lot of stuff.
For someone who has no car, I pack pretty heavy. I recently started into building a lighting setup, and have been putting together an ultra portable but complete strobist kit.
Zenitar 16mm f/2.8
Nikkor 24mm f/2.8 AI
Nikkor 28mm f/2.8 AF D
Carena 35mm f/2.8 (M42)
Nikkor 35mm f/2.8 NAI
Nikkor 35mm f/2
Industar 50-2 50mm f/3.5 (M42)
Nikkor 50mm f/1.8 AF D
Nikkor 55mm f/1.2 AI
Nikkor 55mm f/2.8 Micro AF
Soligor 105mm f/2.8 (M42)
Quantaray 135mm f/2.8
Nikkor 135mm f/2.8 AIS
Nikkor 135mm f/2.8 NAI
Nikkor 300mm f/2.8 ED AIS
Tamron 19-35 f/3.5-4.5
Vivitar Series 1 70-210 f/3.5
Vivitar 85-205 f/3.5
Nikkor 80-200 f/2.8
Sigma 135-400 f/4.5-5.6 ASP AF APO