I am having too much trouble with ordering, so I'll just leave this optional...
My Top 5:
Mexican/Hispanic
Italian
Japanese
Vietnamese
Puerto Rico
Mexico - I grew up basically in this culture although I'm not Hispanic. I would say a vast majority of the people I knew until I graduated high school were Hispanic or at least Spanish speaking, and so I've had a ton of exposure. I love the laid back nature of it's people. I think part of the reason I feel so balanced (compared to peers in my age group) is because of the tropical climate and siesta style culture of where I grew up. Nobody takes anything too seriously... but still family-oriented. Great music, great food, and Tejano/Texican food+culture is a great mix... it's one of the things I love most about where I grew up. Honestly, the attitude of it's people are great... very down-to-earth and friendly folk. They're also very charitable... especially my current neighbors. I'm trying to pick up Spanish for my work and also so I can communicate better with my neighbors...
Vietnamese - Lately I am falling in love with the cuisine and apparently there is such a thing Vietnamese tea? (I think it's just Jasmine?). I also know several folk from this culture, so easier for it to make my top 5, same with Mexican culture... I mostly enjoy it for it's language. It's a nightmare on the eyes written-wise because it has so much punctuation, but it sounds nice on the ears.
Puerto Rico - They are Americans like us, but I like this culture for similar reasons to Mexican culture... except the climate and culture is far more tropical. It reminds me of a cross between Hawaii and Mexico.
Italian - I'm not a fan of the language, but I love Italian cuisine
I'm not Christian, but my grandmother is Catholic and this is my favorite variant of Catholicism. They just seem to have more devotion towards their faith than the American variant... similar to Hispanic culture. Probably because this culture is also down-to-earth. I also really enjoy this section of art history, particularly Italian painters/architecture, etc. I'm not an expert in this area though. Also Italo Disco ftw
Japanese - I fell in love with this culture before I really "knew" what it is. I like it for more practical reasons though the common reasons (anime, cosplay, gaming, etc...). The people are a bit serious, but they have a thick skin (compared to here) and a really high work ethic (though often to the point of health/mental problems). I find their ethos is admirable. I also speak, read and write (though it's weaker than the other two) in this language as I picked it up when I was 15. I have friends I have known 15+ years located there that are practically family... aside from the language, my favorite part of the culture is probably the music. (modern and old)
I would add some African/South American cultures in here, but I have a superficial understanding of those countries, so will leave it open as a special mention... Someone started a thread about World's Strictest Parents and now I'm addicted. They had some African cultures in that series and I was so amused and impressed how strict their cultures are and so pro-education. You know, the complete opposite of the US... which is all relaxed and all about being your best self i.e. Be Oprah. (i.e. be selfish)