Wasn't it Guardiola who argued that Valencia was the best winger in the world at one point, and that Mourinho felt the same and subsequently wanted to sign him for RM, albeit for a RB position. Perhaps not quite as absurd as you would have it.
I completely agree that comparing Nicky Butt to Gerrard is silly. However, what about Scholes to Gerrard? Scholes never had a great career for England. As for great vs good player, I think longevity and contribution to club matters greatly. For instance, Gary Neville was never one of the best players, but many would argue that he is a great player for his overall contribution and longevity. Personally, I think Giggs was a better player than Bale all things considered, and if we are thinking about great players, then Bale is not in that discussion, but Giggs is. To be a great player, you must have made your mark for one of the top clubs and be a legend there. Michael Ballack that you mention is a legend and a great player for Leverkusen; Giggs is for United. Gerrard is a great player for Liverpool (my previous comment was a little silly - still put him behind Scholes, mind you); Lampard is a great player for Chelsea, but Bale is not a great player for RM, and it is debatable if he is a great player for a Tottenham side that has won close to feck all with him in the team. Who is a greater player then, Kane or Bale? IMHO, neither belongs in the discussion with Giggs. Giggs' peak is being downplayed by many now because of his longevity.
To compare their PL campaigns:
Bale:
Appearances:
Goals: 42
Goals per match: 0,29
Assists per match: 0,13
Assists: 20
Big chances missed: 21
Giggs:
Appearances: 632
Goals: 109
Goals per match: 0,17
Assists: 162
Assists per match: 0,25
Big chances missed: 3
Yes, Bale scored more per match, but in all other stats, Giggs is the superior player. Big chances missed was a rather interesting and unique stat (not sure what I put into the unique aspect of it, but there you go). Bale missed 21 big chances, whereas Giggs missed 3 in 632 matches - sounds strange enough. It does tell me, and this is also true from watching them both, that Bale was/is a much more selfish player than Giggs. Thus, Giggs could have scored more goals and thus arguably won more matches than he did if playing similarly to Bale.
Looking at La Liga stats, Bale had a great season in 2015/2016 stats wise with 19 goals and 10 assists. The following season he had 7 goals and 2 assists, then 16goals and 2 assists and 8 goals and 2 assists. In 2013/2014 he scored 6 goals and assisted 3 in the CL, but he never managed more than 3 goals in the CL in any other season. Not bothering to give you all the Giggs CL stats, but they are not much worse - largely assisting more and scoring less - actually being a little inconsistent overall. 30 goals and 53 assists overall isn't too shabby though. Bale has 30 goals and 31 assists in less matches (95 vs 162) -not only Champions League as transfermarkt includes all the European/International, but you get what I'm saying.
So, Bale scores more, but is much more selfish. Other than that, I just don't seem him being a better player, and certainly not a greater one.