Oedi: Thanks for your input, i guess i'll try imperium first then :)
I played all three...
Gensis is the most stable, has the least Bugs and you can play quick and undisturbed.
You can play single maps or a loong strategic sandbox campaign.
The downside is...it's outdated in many aspects UI, Graphics, "animation" and isN't supported any more
MotbW adds some nice features, has a improved UI/controlls, better graphics, real animations... but it plays slower and...has a number of nasty Bugs/glitcheseven noadays,...it's not very common anymore but it still happens that the game corrupts your save...so..make different saves.
Imperium removes the stragic sandbox campaign, adds several new classes&features and every new class gets a storycampaign. I played only the Necrocampaign but the story was below average and overall it was more a expanded tutorial, not a real storycampaign. The Bugs&Glitches that remained at MotbW reappeared at Imperium and some new ones where added, mostly campaign bugs.
My suggestion would be...
If you you're in a "chess"-mood, like strategic games, sandbox and graphic isn't too important to you..play Genesis.
If you need graphic and have the patiance to deal with bugs play motbw
If you need a stoy or don't like strategic sandboxcampaigns start with imperium.