"1st-Gen" meaning any/all groups formed prior to '93. These aren't listed in any specific order, but all fit somewhere in my top 5 list (although My Bloody Valentine and Slowdive are omitted, due to their position as leaders of the genre).
Catherine Wheel (formed '90) - Ferment (released '92)

Catherine Wheel are one of the best examples of the breadth that the shoegaze genre could achieve. While they surely have a very textured sound, often enough with that swirly/heady kind of vibe that shoegaze often gives off, they are also a very progression-conscious, sometimes even rock-oriented, band - there is movement in their music in addition to the haziness that a lot of other bands contained in this category are content to simply get lost in.
dlChapterhouse (formed '87) - Whirlpool (released '91)

Chapterhouse remind me a bit of a mix between The Jesus & Mary Chain's less-abrasive moments and Ecstasy & Wine-era By Bloody Valentine, meaning that there's a bit of a 60's-pop/playful kind of vibe accompanying the (occasionally) cacophonous background music. Altogether, its not at all harsh (as my evocation of The Jesus & Mary Chain may suggest), and I say "remind" because there is far more to this album than what I just said (the vocals in particular I think are quite good).
dlThe Ecstasy of St. Theresa (formed '90) - Sussurate (released '92)

With the exception of The Jesus & Mary Chain (from Scotland) The Ecstasy of Saint Theresa are the only group in this list that falls outside of England... and they are from Czechoslovakia (never saw that one coming). Their sound is a bit like Catherine Wheel's, in that each song has a rather definite progression/s, and I'd say that they are even more into the fusion of shoegaze and rock/indie than Catherine Wheel was - so much so that at times I'm pretty sure Dinosaur Jr. is their backing band. But despite their best attempts at incorporating something that was a bit different into a genre that was, at the time, very rigid, they can play as rigidly as the best of them (track 2 is a wonderful example of that). Almost drone-y, their meditations on distortion, paired with Katerina's almost ghost-like vocals, The Ecstasy of St. Theresa would be one of my top picks for accompanying a hallucinogenic experience.
dlThe Jesus & Mary Chain (formed '83) - Psychocandy (released '85)

These guys are pretty well known, but compared to MBV and Slowdive, they still fall to the wayside it seems. Which is unfortunate, because these guys are basically a perfect combination of MBV distortion and composition and Joy Division rhythm and, maybe half the time, vocals. And they're loud, too. In my opinion, these guys blow MBV out of the water when it comes down to sheer abrasive-ness... yet somehow it comes off as very mellow.
dlLush (formed '88) - Split (released'94)

Lush borders on Cocteau Twins territory at times. That's probably the first thing to get out of the way. They have a very prominent rhythm section, and quite a few vocal melodies going on, with some very trebly guitars contrasting the bass. Distortion wise, they're nothing to gawk at, and so with what I've just said I feel like these guys are a good example of the transition that shoegaze started going through around this time ('94/'95) - it got pop-ier, less distorted, but still has a distinctly distant kind of sound... perhaps that's due to the rather high female vocals, the very-low-presence/high-treble guitar, or the repetitive but not-highlighted use of crash cymbols, but there is something unmistakably shoegaze-y about this album, and its a real killer (especially track 3).
dlUpdate: Chapterhouse link has been fixed.