"I can win" is not a refutation of the claim that investment is gambling in any way that matters. The more relevant question is: does investment reward productivity (i.e. skill, strength, labor) or does it reward ownership (i.e. those who have capital will continue to accumulate capital)? By your own statement, it seems the latter.

All of that money that you've "earned" with investment, where do you think it came from? What do you think you've done to deserve it? If investment is fundamentally risky, then it's an unsound basis for a stable society (i.e. it's gambling); if it's not risky, then you can't even argue that you deserve that money by having risked your own capital.