Tom Hagen wasn't a lead character?! Are you kidding me?

Tom was consigliere to Vito. Tom was the one who handled the Woltz and Sollozo business. Tom was the one who broke the news to the Don on his son's murder. Tom was the interim Don while Mike was away on business in Cuba. Tom got Geary into the Corleone family's pocket. I could probably name a dozen more off the top of my head, but you catch my drift. Tom was a lead character. He wasn't the lead, but he was a lead.

Tom was as integral a part in the first two films (especially Part II) as Mike's character was, IMO. Therefore I see nothing wrong with him being a little less than enthused at making so much less than Pacino. He ranks up there on my list of the greatest actors ever. Seeing as he stated he would have been fine making half of what Pacino made, he wasn't asking for much.