In answer to the thread title " we've been down the back of the sofa, hiding from the chickens"
it all takes place in the same continuity, each game happening chronologically after the last ( difference is usually betweem 20 and 100 years)
though as the game has evolved so has the in-game universe, there is usually an answer one of the game continuity freaks come up with as an explaination for any continuity issue ( and they are very very few and far between).
in order:
riftspace,
Evochron
Evochron alliance
Arvoch conflict
Evochron alliance 2.0
Evochron renegades
Evochron Legends
evochron, EA and EA 2.0 all had very similar universes, with the universe developing for each version, the same is true for Renegades and legends, the basic structure of the universe is the same, but there is more than enough new stuff to keep anyone occupied.
What game would be best to start with?
well that really depends on what you want, if you want to go through and get as much of the 'stories' then go
riftspace, Arvoch, renegades, legends
If it depends on what type of game you want:
missions based : arvoch conflict
freeform: renegades, legends
Which is better renegades or Legends?
silly question, both are fab! I'm still playing ER!
but one good point to note is that Legends has higher requirements, so if your machine is closer to the 'basic spec' of legends you may want to consider Renegades.
But why listen to me?
don't I'm a total fanby

riftspace is available as a free download,
arvoch, renegades and legends are all available as 'demo' downloads, and are only restricted in time and the amount of game you can reach ( no playability is affected)!
so what excuse do you have?
none try them out now!
/end fanboy rant!
Assume I want the maximum space pilot-y goodness.

oh well in that case get all of them!
[Edited on 2-8-2009 by verbosity]