The first Deadpool movie is crass, juvenile, and somehow sparklingly brilliant enough to make you want to stay up late re-watching the second one right now.
The second is crass, juvenile, and a bit more confused and over-complicated, but has enough moments to make you want to watch the next.
The third is crass, juvenile, and just-not-that-funny enough to make you want to skip the next, and wish you'd skipped this one.