You are right! This was a lot harder than I thought. I figured I'd just make a Best Guy Movies list, but even many "guy movies" contain a romance of some kind.
Dirty Harry (1971) Cop, Has a girl, but no real relationship at all
The Longest Yard (1974) Prison movie
Reservoir Dogs (1992) Crime, Not a single female other than extras
Apocalypse Now (1976) War movie
The French Connection (1971) Cops, no real relationships
Monty Python and the Holy Grail (1975) Comedy, just one scene where some horny virgins almost rape a knight
Deliverance (1972) Do hillbillies who try (they succeed) to make a guy their girlfriend count?
Blazing Saddles (1974) Just a couple of prostitutes, no love
Platoon (1986) War movie
First Blood (1982) Just Rambo kicking @ss and taking names
Lethal Weapon (1987) One guy is married and his daughter has a crush on his partner, but the women's roles are very small, just filler.
Robocop (1987) There is some very mild interaction between murphy and a female cop, but nothing close to love. He's half robot!
Kelly's Heroes (1970) War/ heist caper
Mean Streets (1973) Crime, It's been a while, but I don't remember any romance in this one.
The Seven-Ups (1973) Cops, I don't remember a romance.
Patton (1970) War Movie
Runaway Train (1985) Prison escape, I don't remember a romance
Enter the Dragon (1973) Just Bruce Lee kicking the crap out of anything that walks on two legs
48 Hrs. (1982) Buddy film/crime drama. Eddie Murphy trie to get laid, but he just got out of prison, what do you expect?
Papillon (1973) Prison, escape
Shaft (1971) Cop, Don't remember everything, but I'm gonna guess that Shaft had some ladies, but no love interests
Big Wednesday (1978) A tale of surfer's lives. The marriages and girlfriends take a back seat to the comraderie and male bonding
The Last Detail (1973) Sailors escort a young man across country to prison, Drinking, Whoring, a brief romantic connection, male bonding
Saving Private Ryan (1998) War Movie
Full Metal Jacket (1987) War movie, brief whoring
The BigLebowski 1998 Some sex, but no real love. Weed smoking, White Russian drinking, bowling
The Untouchable 1987 Cops/crime. Eliott Ness was married but that was just background stuff
Predator (1987) All action, with a hint of romantic connection
Alien (1979) / Aliens (1986) Some romance hinted in Aliens
American Psycho (2000) A serial killer, not very romantic
Training Day (2001) The Girlfriend and son relationships were there, but never deeply expanded on. They were just dramatic devices
Collateral (2004) Crime drama, not much romance here
300 (2006) Couldn't get into it. Seems to be a fan favorite, mostly action, don't recall much romance
The Usual Suspects (1995) Crime drama, mystery. Mostly just guys.
Das Boot (1981) Submarine films are dude fests
Crimson Tide (1995) Sub Movie
Hunt for Red October (1990) Sub movie
U571 (2000) Sub movie
Glory (1989) War movie, All black battalion in the Civil War
Miracle (2004) Hockey film, coach was married, but they didn't explore that too much, just a little bit.
Rudy (1993) Football, some romance was there, but very much in the background. It basically disappears by the end.
Cool Runnings (1993) First Jamaican bobsled team. you heard me right, Jamaicans bobsledding!