I haven't gotten to Kryceck and Spender yet, but have heard good things about Krycek.

I have some things I could say to defend Supernatural, but I really don't like the show enough to bother :D

Normally when a show's central relationship is an odd couple the differences are made explicit by contrasting actions, but in Mulder and Scully's case, the differences are intellectual and they otherwise have a similar modus operandi. That's what enables the Beckettian humour of the show - the fact that they stand around in matching outfits and set their philosophies on each other.

Yes, I like that too (though I would not have said it so well :))