Well, to be a Kage, I suppose that he also had 2-3 elements jutsus at least and had surely some nice jutsus. I' agree that with 6-gates is a bit harsh against Minato but apart FTG, he surely knows lots of jutsus, excellent at fuiinjutsu, seemed good at taijutsu, don't know about genjutsu and was prime in his space-time ninjutsu. He also had a lot of chakra reserve as he did two seals and was still talking while sealing Kyuubi and did FTG lots of time before doing that on that night.
I think, he can beat Guy. It will be tough but he can do it. YOu should atleast have just said no FTG as space-time ninjutsus give two handicaps to Minato (no FTG and frogs summoning) but also one to Guy (no turtle).
It could go either way but Minato can pull it off even without FTG. You need to accept that what made Minato great is that with two jutsus that required very little chakra consumption (FTG and Rasengan), he could pwn almost anyone but still, he surely did know lots more of that especially elements jutsus and fuuinjutsu. Also, he has a higher IQ than Guy.