Fabianski or Green... tough choice. I'll go with Fabianski. The grass isn't always greener...
Right back is a difficult one. I could say Coufal based on last seasons form... but if we're basing it on one season then I could also say Schemmel. I'm going to say Breacker as he was dependable for multiple seasons.
Left-back... it has to be between Dicks and Cresswell surely? Cresswell has the greater footballing ability, has been consistent across many seasons and was part of the great teams we had during Allardyces sakho/valencia season, Bilics first season, and two good seasons with Moyes.
Centre-backs... we've had a lot. Peak Collins and Gabbidon were both really good. Ferdinand, Bilic, Reid, Zouma, Martin, and Ogbonna have to be in the reckoning too. Ferdinand was at his best later on after he left us. Same as Lampard. I'll go with our current first choice pairing of Zouma and Ogbonna. Controversial?
Defensive (or box-to-box) midfielders... Rice, Parker, Foe, Song, Kouyate, Bishop, Allen, Carrick, Soucek. I probably should go for Rice and Parker. Both clearly our best players during their respective times. I'll go with Song instead of Parker though as I thought he was brilliant the first time round and a joy to watch. No so much later on.
Wingers... Payet would be on the left for me. On the right... could be Sinclair, or peak Antonio, or even Bowen. I'll go for Bowen - I like him.
Attacking midfielders... Could Di Canio play number 10? And then we have Berkovic, Benayoun, or maybe even Lingard. There's Lampard too. I'm going to go with Lingard.
Striker... Arnautovic, Antonio, Ashton, Di Canio again, Tevez, Bellamy, Hartson... we've had a few decent strikers. For me it's between prime Arnautovic and prime Ashton. I'll go with Arnie.
Almost a best of Moyes side. Slim pickings at full-backs though to be fair. Also, as tempting as it is to pick older players due to nostalgic sentimentality, the fact is that many of them were part of a West Ham side considered to be a soft-touch and lost a lot of games. Also some players reached their best for other clubs after leaving us. These players were all important players in West Ham sides that did well. They were feared. I'll be honest, I'm not entirely happy with Breacker at right-back but there's no player that's really been outstanding there for more than 1 season.