The examples don't hold in most jurisdictions (except for the stock market and if short sells are allowed).
replyAll of the three categories are defined as gambling in pretty much all jurisdictions across the globe. However, they are classified as different types, e.g. roulette is closer to slots than poker is. Then poker can be "cash tables" vs "tournament". The main classifier difference is "game of chance" vs "game of skill", yet there are lots of nuances.
As I stated in my comment, they weren't examples of the legal definition of gambling. What the law says something is can often differ greatly from the every day understanding. The legal definition can also change according to the whims of the legislature while the every day meaning tends to stay more static.
reply> Poker - not gambling
replyhttps://en.wikipedia.org/wiki/United_States_v._Scheinberg
In the distant past of 2011, offering online poker to Americans, even from overseas, brought serious Federal prison time. That was before the lobbyists got to work.
> Stock market investing - not gambling
replyThat entirely depends on the asset classes you invest in. Proper stonks? Sure, that's not gambling. But as soon as you enter the fun world of derivatives and daytrading...