The same developpers as the first opus, though.
Yes, they are similar. I love both. There is some differences (for example, Mario golf show the falling point of the ball, HSG the point after rebounds, of course neglecting wind, lie and ground...). Mario Golf has more options, like time attack, ring shots and such, but it's a pity that there's so few courses.
Online could be an improvement, Fore's online mode is a catastrophic (fall in a bunker in fast mode, and you will be deconnected by "time over", you've only a board, and you can't even look at others...)