Just look at it. :D It's so awesome and just... wow. It's one of my favourite legendaries too, and I have a lot of fond memories of Pokemon Crystal (which is also my favourite Pokemon game overall). The other two don't just have the same effect on me as Suicune or, as someone I know close to me likes to call it, tissue butt does. :'D
Definitely Suicune for me. For pretty similar reasons - I had a love affair with Crystal growing up. Probably my absolute favourite Pokemon game.