Personally, I don't really see how a Glock could be made "better" looking, without compromising its quality.
Rounding off the slide edges would lighten the slide, with all that entails. A square cross-section is heavier than a rounded one. Heavy is good. The Glock has lots of weight where it needs it, and less weight where it doesn't.
The heavy slide decreases the felt recoil, and it keeps the slide velocity low and the cycle time long. Long cycle time allows the use of weaker recoil and mag springs, and increases reliability a lot by decreasing magazine sensitivity. It's mainly the cycle time that makes Glocks so reliable.
In almost all handguns, the magazine is the weakest link. If you get any jams, the first suspect is the magazine. Why? Because cycle time in handguns is very short.
Look at a blowback submachine gun, like an M3A1 "grease gun," or a Sten. Those will work with any crappy, rusty magazine you stick in them. When you've got a 2 pound bolt moving almost a half foot with each shot, and a cyclic rate of only 450 shots per minute, the cycle time is extremely long. So the magazine can feed rounds at whatever speed it likes, and the gun will work fine.
But most pistols have very light slides that only travel an inch and a half, very high slide velocities, and a cyclic rate of something like 2000 shots per minute. Very short cycle time means the mag has to feed rounds at a very specific time. End result is, to get a 1911 to function reliably, you need $50 magazines. Or maybe really old ones, from back when guns had hand-fitted parts, though those don't always work that good. On the other hand, a Glock will work with a much wider range of magazines. If a 1911 jams, switch mags. If a Glock jams... Glocks jam??? Similarly, 3" and 4" 1911s tend to be fairly unreliable, while all size Glocks are very reliable. Mostly cycle time.
Really, the slide is the only part making the Glock "ugly." Just round out the slide a bit, maybe come up with a catchier name, and everyone would be all over them. But the square shape is really the biggest advantage to the design. And the polymer frame complements the heavy slide, preventing the entire gun from being too heavy.
On the other hand, the square edges apparently make the gun look and feel thick. Even though a 1911 slide is 0.94" thick and a 9mm/.40/.357 Glock slide is 1.008" thick (about a 1/15" difference), everyone seems to insist Glocks are way thicker somehow.
Also, the light polymer frame has less inertia, so it has less of a tendency to stay in place while the slide recoils. That means you need a slightly stiffer wrist compared to a steel-framed auto, when shooting weak ammo. Easy solution is to use stronger ammo.
Relatively small disadvantages, considering the benefits of the long cycle time and light weight.
Of course, some "expert" with high speed cameras and junk will probably say I'm wrong on the cycle time. I just know, from personal experience, that Glock slides are really heavy compared to most other guns, and it's easier to see them move while firing.
