SSJ1 was a milestone, but personally, I think the presentation of Gohan SSJ2 was the best-executed transformation, with the soundtrack, the scream, the context, and all.
Dragon Ball understood the value of the "react" long before it became popular. Watching a transformation with other characters reacting to it makes it much more epic.
This was absent in Gear 5. Only Kaidou saw the transformation (much later) and didn't care much about it; he only commented on the fact that Luffy was still alive. It's a shame that not long ago, we had Luffy mastering Ryou, which I found incredibly epic, even though it wasn't a transformation. But now, when it would have been even more important..., that's what we got to see.