Not sure this goes here but...
I have a game partially planned out and written but have a few issues.
The biggest being what system to use. The game's plot is: a group of people is gathered by a mysterious government group to investigate strange artifacts that have been touched by evil. That's the W13 part, the CitW part is that the items are from horror legends/movies. Like in the movie the artifact will effect the players as if they're in the movie.
There will be various settings from urban to rural to Scooby Doo-esque.
I at first thought D20 or AFMBE because I want to mostly have action based characters but I want an easy to use system that leaves freedom to use multiple villain types and settings.

In reply to SeanoftheUndead  (msg # 1):

This is a cool idea. You might want to check out Monster of the Week (listed under "Apocalypse World Engine" system on DrivethruRPG, also sometimes listed on sites as a "PbtA" or "Powered By The Apocalypse" system game.) It specifically suggests a "supernatural investigative agency" type of game.

You might also be able to adapt Call of Cthulhu/Delta Green to suit your purposes.

My last suggestion would be to consider Fate Core/Accelerated, which is a generic system that is less crunchy and combat-centric and more storytelling-oriented. You can adapt it to pretty much any setting. The Librarian and the subsequent Librarians TV show are based on a Fate campaign that the creator of the TV movies and TV show ran with friends, and frankly, the concept is very similar to Warehouse 13. To add to the horror aspect, you could add a "Fear" stress track in addition to the normal health and mental ones.

I find that just about any system can be adapted to any custom setting.  The difficulty becomes the GM's level of familiarity with the core system, and the level of complexity of that core system from the perspective of the players.

Newer systems are generally less complex with fewer moving parts and thus easier to convert.  Something like 5e D&D for instance requires almost no system mechanical conversion to adapt to a setting like the one you describe.  At most you adjust a few word choices to feel more modern and sub out some light weight super science for magic as a cosmetic change.

On the other end of the spectrum there are always system mechanics like GURPS that have done all the conversion already by being so complex it starts with every possible feature, but almost no players understand how to use it.