as a huge Fan of Robinson Crusoe I would like to try out other Games by Ignacy... Imperial Settlers And 51st State seem to be pretty similar - so if we arme just Talking about Solo Play, which one would you recommend? I think I prefer the theme of 51st State a bit, IS seems to be more elegant though (And a Game that I actually might Play with my GF from Time to Time).
I would go with Imperial Settlers. I have tried both solo and they are pretty similliar (this same almost) except the end game trigger which in 51st might be better for multiplayer but is a little worse for solo. In IS you will have more fun in building engine for 5 rounds.
I own both and love both for solo. If I could only have 1 I would probably pick imperial settlers. The theme is a little more pleasant and the solo AI and bit easier to play against. The solo AI in 51st state can take out some buildings pretty easily.