Supplements for me have their greatest benefit if they effect my mood. Outside of the basics, protein, vitamin, fish oil, anti-oxidants, it comes down to mood enhancement. Several products I have used have altered my mindset, kept me focused, and improved my daily desire to hit the weights. That to me is a good supplement, even if it doesnt do anything for my muscles in particular lol.
My ultimate love is Phenibut! That stuff turns me from silent madman, into social don suave.
I have had several stacks I put together for myself that made a huge difference in the gym though. But no supplement will do crap for you unless you are eating in a way that gives your body the raws to create a masterpiece.