You don't have to compare intelligence to notice that you're edit: r/smarter/more intelligent (or that others are r/smarter/more intelligent than you). Especially when you're working together with someone for a long time.
After a while it's like knowing you're shorter/taller than someone - you won't notice and you might be wrong if the difference is small - but when it's a large difference it's just something you know even if you never consciously thought about it.