IMO Spies is exceptional rather than decent. He's definitely deserving of a shot at MotoGP on a good bike but as you say, success is not guaranteed and it's definitely easier to get a ride than it is to keep hold of one since there are always so many "good" riders waiting for their turn.
It's a shame there are so few "top" rides in MotoGP at the moment. Nobody wants to see someone as promising as Spies scratching for results on a satelite bike for a couple of years.