Ho-oh, but I would choose lugia because I like ho-oh 1000x more.

Say whaaaaaaat?!

No, i say this because if you pick up silver or soul silver, you can get lugia, which is very good anyway, and then you get ho oh, the most awesome one ever, at level 70 after beating the elite for as sort of an ultimate final boss. that is the best way, imo, to experience ho-oh.