Angling joysticks seems like a "space-solution" to many, but in reality no one stands shoulder-to-shoulder on real 4-player cabinets. If you keep the outer controls relative to the screen, a player can stand anywhere (including off to the side) and still know "which way is up" (see: Gauntlet). When you angle them, you are pretty much counting on someone to stand in a very specific spot, which is actually counter-productive, since now if someone moves, there's a whole lot of discombobulation.
Secondly, don't fall into the trap of "he/she will feel the corners and figure it out" or "they'll look at the joystick bolts". If you have people over, they won't know to do that. Up towards screen, however, is always intuitive.
If you look at actual 4-player panels, you'll notice that the buttons on the outer controls are not directly to the right of them. They can be below, above, etc. That's because 4-player games are not complex affairs and you can save space by placing those in unorthodox positions.