I think it partly comes with being related to an architect. I've heard of other families who did this, too. We would drive around in old neighborhoods, checking out the architecture. From the time I hit double digits, I could tell you what I did and did not like about the structure of the houses we saw. Developing a discerning eye, and being able to name exactly what it was that appealed to me, was not only fun but a great basis for conversation. Also.... open houses are a fun chance to dream, even if you're not related to architects ;) I love the Arts & Crafts era, and a California Craftsman bungalow would definitely be a dream home for me. The Victorians hold their charm, but don't always hold up that well. I almost rented an apartment in one, but it wasn't meant to be. Eichlers, with their mid-century modern vibe, have a special place in my heart.
... and that's just the exteriors! Feel free to share some favorites.