I know HRE is an elected position, but as I read more about the power of the Dukes, Clergy, etc. I am not convinced it was a good thing to be Holy Roman Emperor. It seems like it took a lot of capital (bribes) to be elected, in some cases putting multiple generations into debt to become HRE, only to continually having your power ultimately controlled by the electors, church and other, Dukes, Kings, etc. It seems being a Duke of a controlling region was a better deal. So... why?
Because Emperor was the ultimate feudal title and the highest honour imaginable. Until relatively recently (with the coronation of Napoleon) there were no "emperors" in Europe, there were only ONE Emperor, the Holy Roman Emperor. He was recognized by the Pope as successor of the Western Roman Emperors (that's the notion of translatio Imperii). And so was considered, depending on what era we're talking, either as the sole legitimate ruler of Christian Lands (for the Early Middle Ages) - strangely few beyond Germany and Italy agreed - or as the First among the rulers of Europe, having precedence over all the other monarchs.
Being emperor was costly and yes it did not bring a lot of real power (especially in the late Medieval/Modern periods) but the prestige and the influence that came with the title was immense and beyond anything else. As the Emperor you were not simple a powerful ruler, you were -again, on paper- the chosen protector of Europe and (according to some emperor) the temporal equivalent of the Pope.
Also keep in mind that an Emperor was always a powerful feudal lord, the imperial title gave them an very strong influence over pretty much all of Germany and northern Italy, influence that they could not attain otherwise (as the Emperor was also nominally king of Germany and Italy), look at the Hapsburg during the 17th century, due to their title they saw themselves as the rulers of German lands (that's one of the causes of the 30 Years War by the way).