That's too broad of a generalization. p2p is AWESOME for latency since every server added adds latency. What you are talking about are probably p2p networks with multiple users (based on your shooter reference) and the problem is of home connections and bandwidth since multiple users that all need to connect to everyone doesn't scale.

So for your example: One on ones over p2p are optimal, but p2p matches with more than 8 players are suboptimal (I pulled the number out of my ass it depends on the protocol and usecase)