This is going to sound snobby, but until you’ve played metal gear I don’t think you’ve experienced the pinnacle of stealth. That series basically defined (access arguably perfected) the third person stealth action genre.
If you don’t want to play them all, I highly recommend metal gear solid 3 and V. But the “demo” ground zeroes game is a great way to get a feel for the series in a more contained experience
Runner ups in my mind that others mentioned:
Splinter cell
Thief
Deus ex (you can choose stealth in this game but it isn’t specifically a stealth game imo)
Dishonored (superb)
Prey (essentially dishonored meets system shock)
You gotta go grab some metal gear, though. Oh how I wish I could experience those games for the first time again.