NFL = It was super easy when we had the best RB in the NFL, but that's a short shelf life. It actually might be Cousins, even though he is overpaid. There might be nobody more overpaid, but underappreciated than a legit, but not great, NFL QB.
NBA = I think it is probably Jaren Jackson Jr., but he has his role. So I'll say it's still Draymond Green. The couple of NBA podcasts I listen to say he probably has the highest defensive IQ of any NBA player ever. In a different era, that would be WAY more valuable. But I'll still go with him.
MLB = I think relief pitcher Anthony Misiewicz is the only active MSU player in the majors
NHL = Semantics. Duncan Keith has the best career of any player still playing. But he's also 40, so Torey Krug is probably the best player right now.
Other = James Piot won the US Amateur, and then beat the Euro amateur for the world amateur title. So he's still at MSU for now, but is probably the best MSU athlete across all sports right now. Very excited for his trajectory