Imho the definition of minor is rather relative : Portugal is rather small, with just 4 or 5 provinces at start. Venice is about the same size at start, but lacks the initial flow of explorers and colonists.
I must admit I rather take a liking to every nation, major or minor, I have played thus far. The combination of size, position, colonists, explorers and leaders makes every game special and poses its own unique challenges.
The risk style of play (conquer! kill! annex! conquer! kill! annex!) appeals less to me than an economic / peaceful style of play. I feel this makes all nations blend into the same pattern.
I liked the Mughals when I played them (just finished them, report to follow). I am also liking Venice, and when I played the Netherlands in the age of Commercialism I liked them too.
I hope to play France, Sweden among the majors somewhere in the future.
Among the minors, Oman is attracting my attention after a recent issue of the national geographic. Or perhaps Morocco.