England is always the strongest in games like these but through my gaming history I’ve always been drawn to Spain or Italy
I realized a while ago that with pretty much any medieval-era strategy game (Crusader Kings 2, Medieval Total War, etc.), I avoid England and France on my first few playthroughs. I think it's because those two countries seem to be the ones most often (and/or stereotypically) associated with the medieval period, so I automatically try to play as a different nation.
Like yourself, Spain has long appealed to me, or even just the Christian powers on the Iberian peninsula in general. The Byzantine Empire is another one that always fascinates me, though it's usually somewhat overwhelming and/or intimidating trying to run a larger nation when you're first learning a new game -- particularly one like Byzantium, which sat at the crossroads of the "known" world, and thus had many issues to deal with (even setting aside its own internal court intrigue). The Levant is, of course, an interesting place to start a campaign in, with Egypt (Fatamids) being a particular favorite of mine. And in more recent years, I've been increasingly curious at giving someone like Kiev or Novgorod a go. (Hmm...)
Btw my playthrough was Genoa
Castile is the very old CK2 playthrough
Ach, I'm an idiot, you're right. I don't know why I had Castile stuck in my head (other than, of course, that it was a very good AAR
).