I have been a fan of acrhitecture since I was a kid (I think it was because Mr. Brady was an architect...). I wanted to be an architect but had a bad experience with a drafting teacher in high school...
There are a lot of styles that I like but right now I am going through a modernist phase... I really love the clean lines, the open spaces, the mixing of materials... Unfortuantely this style is large ignored in favour of replicating Victorian style suburban housing... developers are really caught in a rut.
I can appreciate victorian and edwardian styles... I just think there is so much more out there... It's just that we seem to associate these particular styles with quality. Add to this that the suburbs are examples of horriffic urban planning to begin with and you get the thing we call suburban sprawl... Ghastly.
Here is an example of high density modern housing... (I think these are in Amsterdam).
As far as larger buildings are concerned, I have to say that I love the Chrysler Building and the Empire State Building in NYC... but also have a fondness for more simpler designs like the TD Towers in Toronto (designed by Mies van der Rohe)
Royal Bank Tower
Detail
In answer to what makes a building memorable... I would say it is good design that makes it memorable. Something that is both beautiful and functional... something that works in the environment in which it is situated (whether that is a juxtaposition or a seamless melding).