I love Predator 2, but I never felt Danny Glover was a great choice for Harrigan. Dutch was like the prime example of human ability (the character) matched up against the ultimate hunter. Harrigan was a mediocre follow-up, as played by Glover.
Think of the scene towards the beginning of the movie, where they see the drug cartel guy hanging from the ceiling. Danny calculates the guy's weight and the distance to the ceiling and turns to Harrigan and says "you couldn't drag him up there!" My initial reaction, even the first time I saw it in 1992 was, "no shit, he's a regular guy like the rest of us."
The comment was obviously written to make Harrigan look stronger and tougher than he is...and he's honestly just kind of a chubby older guy.
So yeah, Danny Glover was not a great choice for Harrigan, but he's what we've got. I love the movie despite Glover, not because of him. He's a good actor, and I like him in a lot of other things, but he wouldn't have been my choice.