What system for spy games?
There are any number of espionage rpgs out there, including Conspiracy X, Corporation, Danger International, Espionage, James Bond 007, Mercenaries Spies and Private Eyes, Nights Black Agents, Over the Edge, Spycraft and Top Secret. For that matter, D20 Modern also covers the genre, although it includes monster elements (if you want them).
I couldn't say which ones of these are still being published or even available as PDFs. So I'd say consider if your players are going to have copies of the game. If you go with something like GURPS or Spycraft here on RPoL, you'll probably only get players that actually have those games anyway.
The other consideration is the mechanics you want. Most of the games have cinematic options.