Arrowsmith, written by Kurt Busiek, is an excellent story. It's about World War I on an alternate Earth where magic was developed rather than technology. Soldiers fly around with spells that grant them the powers of little dragons and fire bolts of magic energy from crossbows and stuff. Plus there's a great story centering on Fletcher Arrowsmith, an idealistic kid who joins the Army with dreams of adventure and is forced to deal with the harsh realities of warfare.
JLA/JSA: Virtue and Vice is another good story. It's written by David Goyer and Geoff Johns and features the JLA and JSA teaming up against the Seven Deadly Sins and some other classic villains.
Avengers Forever, also by Busiek, is the absolute best superhero work Pacheco's ever done as far as I'm concerned. He was pretty much at the top of his game there, and Busiek's a huge Avengers/Marvel history buff, so if you're an Avengers fan it's one of the greatest Avengers stories you'll ever read. It takes a bunch of seemingly disparate elements from the Avengers' past and future and ties them all together into a thoroughly entertaining story.
