Investment and gambling is different, also the word "gamble" is a very broad word to begin with. I guess the right term to use when you're using your money in an investment is "risking" and not "gambling" your money because you put it in a game to earn money.
The other way to determine the difference between NFT games and gambling is that NFT games assures you to earn money once you started while in gambling, it is the complete opposite.
NFT games who offered Play to Earn set up indeed gives you that opportunities, once you started you'll received amount of compensation,
while in gambling if luck is not on your side it will going to get the money out from your pocket without
any way to recover it unless you'll try again and put more money on it.
Both have risk but if you think wiser investing with NFT games might have some good edge as hypes really bringing
this assets to the next level inside crypto industry.