I played Doom, Duke, Descent, HL, CS, MoH, the list goes on.
I was a keyboard turner for a long time. Once I got used to mouse aiming, I got banned regularly for using aimbot (hint: I painted a dot on my screen).
I used arrow keys for a long time. Once I switched to WASD, I stopped sniping and got banned regularly for wall hacking (hint: I used headphones and listened to footsteps).
I stopped playing FPS a few years ago. Too much whining.
Still, unless something fundamental has changed, there isn't a significantly better combination for keyboard/mouse (the universal standard for all personal computers today) than WASD for movement, mouse for aiming. All your important keys (movement, jump/crouch, reload, weaps, vision, chat) are accessible without moving your palm. Your free look, aiming, maybe reload, tab weap, zoom, secondary, can all be done with the mouse.
WASD is default partly due to tradition, but mostly due to functionality. Notice that every keyboard replacement on the market share the same qualities: Lots of easy to access keys with finger location readily available by touch. The left side of the keyboard shares those qualities. The arrow keys are simply too isolated for games that require more than 10 keys.
With FPS gamers stressing over latencies measured in milliseconds, it's much better to simply have all your keys accessible without moving your hand. Also, WASD setups are less likely to mishit because they have so many keys within reach without moving the hand at all. Using arrow keys for movement in certain games will increase the number of mishits because you have to move your hand to reach keys. The human mind is better able to process movement of only the fingers as opposed to fingers + elbow/wrist. There's a reason all the popular keyboard replacements on the market are designed to have the hand resting at all times.
I'm almost willing to bet nobody will completely read this post.
The keyboard was originally designed for typing. Qwerty layout came to be as a way to minimize collisions between typewriter keys. As a side effect, that also increases typing speed since you're far less likely to use the same finger for two letters in a row. However, the qwerty layout was never verified to have the absolute minimum number of collisions. Also, a hundred years or so of evolving language would pretty much destroy any probability test on letter use. Still, like many inventions, it has worked "good enough" for so long, which means that manufacturing and re-training costs are minimal. Designing, implementing, then training a "perfect" evolving solution has so far been cost prohibitive.
Notice with a keyboard, the most commonly used function keys (keys other than alphanumeric) are placed within easy reach and the most often used (space) is the largest. Large keys at the edges reduce the chances of mishits. The 6 insert/home/etc keys, arrow keys, function keys, and numpad keys were added later. Arrows and insert/home only came with computers (along with ctrl, alt, esc, etc). However, since they were rarely used, there was no reason to keep them as easily accessible, especially considering the standard two-hand setup with index fingers over F and J where you can easily reach more often used keys like Return/Enter, Backspace, Tab, etc. The numpad is yet another separate section because the proper way to use it is with one hand (that's why there's a ridge on 5) so since you're already breaking the standard two-hand posture, there's no reason to try and fit it around the standard alphanumeric.
That being said, keyboards are not the ideal interface for gaming. A full VR suit with equivalent laser weapons would come close. However, since it's a part of every single personal computer on the planet, developers have little reason to require anything different. Flight sim buffs and hardcore gamers in general will buy their own replacements for that extra edge and experience. Everyone else (the vast majority) will go with "good enough" and keep the extra money in their wallets and the extra real estate on their desks.
PS: I really want to see someone access 50 keys with their hands over the arrow keys. Either the fingers would be so long the keyboard would probably be impractical or the keyboard so small the keys get hit 3 at a time. I have small hands (even though I'm 186cm) so from the arrow keys with 3 fingers on < ^ and >, I can only hit 11 keys. To hit 50 keys, I would need another 3cm of length on each digit. With only 1 cm more length, I can hit maybe 8 more. From WASD, I can hit 26 keys without moving my hand.