Can a 5V regulator connect directly to a voltage divider to obtain a 2V output?
This idea will work providing you don't need to supply more than (say) 20 mA of current at 2V to other devices because it's likely that the op-amp wouldn't be able to do this - some op-amps will supply (say) 50mA such as the AD8605 (from memory) of course.

DC offset is an issue if you want to use an op-amp so check the data sheet.

Why not find an adjustable regulator that can do the job - most are able to supply at least 150mA and can be adjusted by a resistor divider from about 1 volt upwards.