Dan Rather ain't all that impressed by the Giants' win Monday night -- he thinks they're still awful ... but he's happy as hell for Eli Manning!!
The CBS News legend watched Eli turn back the clock on 'MNF' ... leading a game-winning TD drive over the 49ers late in the 4th quarter -- and dude couldn't have been more proud of the QB.
"I'll tell you what, whatever you think of the Giants -- and they are terrible -- I love Eli Manning," Rather tells TMZ Sports.