The base game won't give you global stats tracking but there's a pretty active community over on speedrun.Com, which is where most people compare their times and achievements. You can check out mission completion stats, level records, and see how you stack up against other players there.

While you're playing, some custom mods will show you session stats right after finishing a mission, which is neat for immediate feedback. The steam version keeps track of basic achievements, but if you're really interested in seeing how you compare to others, jumping over to speedrun.Com is your best bet. They've got everything organized by category, version, and mission type so it's easy to find what you're looking for. Those external rankings are where all the serious players hang out, and they're pretty thorough with tracking everything from completion times to specific challenge runs.

The whole setup works pretty well even without built-in leaderboards since the community's really active with keeping everything updated and organized through these third-party sites.