Oh man, Pentium II-IV was when my parents were totally into Gateway. Are you thinking of some of the later G5 or early G6 systems in the box case, or the later G6 systems from when they rounded everything out and had the removable face-plate (1)covering the additional drive bays, or from just after that when they were boxes but with rounded fronts again?
Back when we got our G6-400, the "family computer," it was of this particular style:
Later on, a Select 700 was bought for my room, it was of this style:
There was also the Gateway Destination, which certainly started ahead of its time, and the ProFile series, which never seemed too commercially successful, but intermittently had pretty good designs. There was also the Gateway Astro, which was pretty clearly ganking a specific design, while remaining true to its "I'm from a '90s PC vendor" heritage, which made it interesting, if not exceedingly boring. Although, they do say that every repost is a repost-repost.
(1) I am a reasonably big fan of faceplates that move away to reveal inner workings and/or additional drive bays, especially if they're bays you can't make pretty. Gateway did a lot of this. On the fatter curved minitower, you could also hang the faceplate to the front of the system when you were using something behind it, so as not to misplace it. By the time the Pentium 4 was happening, Gateway had built several of their systems with flippy lids covering all of the drive bays.