Marquee signing = Exceptionally popular or skilled.
It's a very American thing that has crept into our vocabulary. The definition above is from a Google search, and you could basically call a shit load of players marquee signings.
For me, the popular bit of it would only classify as marquee if the player was globally popular, and I'm not sure Sane, Stones or Jesus (not the fucking Nazareen) would classify as globally popular. I also wouldn't put Gundogan in that bracket either.
Now, I'd be more circumspect with how to use marquee signing for exceptionally skilled. Looking at YouTube (!) the Jesus (again, not the bloody soon of God) fella could qualify, and so could Gundogan when you see him on the ball. I wouldn't put Sane or Stones in there for being exceptionally skilled.
Therefore, stop fucking arguing about who is, or isn't, a marquee signing, as I've nailed it above.......