Humans are tough in a different way though. Of course a lion is far stronger and more agile then any human, however a lion lacks the phisical endurance to sustain phisical exertion over a long period of time, and need to eat A LOT to maintain themselves working at an optimal level, plus, they aren't very adaptable and will succumb to changes in environment and climate rather quickly.
On the other hand, many indigenous human populations from across the whole world have been known to stalk prey for days at a time and maintain a high level of phisical exertion for hours. There's also new studies that show that humans can be as strong as the big apes, but we have a "neural limit" to how much muscle fibers we counciously use at a time, since our brain evolved to make more fine motions rather then the all our nothing explosive muscle usage of gorillas and chimps, so our brain limits the ammount of muscle fibers we activate at once. That neural limit is only supressed at times of great danger, which is why we'll ocasionaly find news articles of normal people doing incredible feats of strenght in certain dire situations, like that guy who pushed a huge bolder off his body and over his head when he got into a hiking accident.
Anyway on topic: X3 did humans decently I think. You get the more "vanilla" humans the argons which got separated from the earth based humans for such a long time they might be considered a different species, and follow the diplomacy and trade route, and the earth based humans who are very defensive of their systems, suspicious of other races and have very powerful ships and weapons of their own design, which makes most races fear them. Additionaly most of their vessels can't use commonwealth equipment, they can only use human produced equipment.