Where can I see my perfect games in steam?

Steam does not provide such functionality. You need to use a 3rd party tool. One of such websites is AStats.

Once you've found your profile, you'll be able to navigate to the page with games completed 100% like in this screenshot.

I can offer an alternative solution. Use this script:

Steam-Zero.

December 2020 answer: Steam now has a "Perfect Games" tab that you can access from your profile, e.g:

https://steamcommunity.com/id/{username}/games

https://steamcommunity.com/profiles/{profile-id}/games/