The ES is definitely the better of the two. The only GS worth having is the GSF otherwise there is nothing that the GS does that the ES doesn't do as well. Both are similar in size and both are luxury cruisers.
The GX on the other hand is an archaic tractor that is laughably terrible when compared to the Mercedes GLS, Audi Q7, and the coming BMW X7 (I'm assuming). The 3 row RX is very likely a stopgap until something worthy of mention can be produced.
Until then, enjoy that fire-sale discounts on the GX and GS if they are your cup of tea. For me, they both cannot die quickly enough.