I'll just let you do a search. Here's a few that didn't require any user intervention:
Witty worm, population of around 12,000 installations of ISS security software. Infected all vulnerable hosts in less than an hour. The worm was released the day after a patch was released for the exploit, and most administrators had not yet applied it (a good admin doesn't just patch his enterprise software without testing first).
SQL Slammer, population of maybe a few million installations of MSDE (often installed as part of a third-party software installation) and SQL Server. Infected up to 100,000 hosts within 10 minutes.
The 1998 AutoStart worm spread rapidly through the Mac community even in the age of disk-based transmission. The Mac population was at rock-bottom at this point. The prior year Michael Dell had famously said that Apple should close shop, and the successful iMac wouldn't be released until months later. Apple was at the height of its irrelevance and obscurity, and yet someone bothered to release a successful auto-spreading worm for the platform.
If you want a perfectly secure computer I suggest filling the case with cement and using it as a doorstop. If you want to actually use your computer, then for whatever reason OS X has the better track record of real-world security.
Ok now post a link to a virus that attacked the OS and not an application.