Can a 2000 watt portable generator run a small electric chain saw that's rated at 3.5 hp?

I think something is fishy with the numbers. What actually does the nameplate say? 3.5 Peak HP?

While there are 746 Watts/HP, this isn't generally enough to start it. 746*3.5 = 2611 and 2611/120 = 21.758 Amps.

So, something is fishy.

3 to 5 times the HP rating for starting but it depends on the motor. The chain saw will mostly be started unloaded which will help.