Well that's a hard choice for me since I grew up in the 2000's I have always loved my g3 are my favorite and I have never own a G1 or G2 playset so I'm going to do this by generation
For g1 I'm going to a agree with everyone on Paradise Estate it's much bigger than all the other sets they made
For g2 I'm going to go with the garden playcase I love the color and portability of it
For g3 I'm definitely going to go with Crystal rainbow castle be because it so big a beautiful I have been waiting this set forever I'm still looking for it
G4 they are so many playset for g4 it's so hard to choice but I have to say my Seaequestria is my favorite it's top with Canterlot Castle
Can you see running theme here I really like places that are big gorgeous and beautiful