I actually played Omikron right after Outcast, a friend (who did not play Outcast) told me it was the coolest adventure game he ever played. I remember seeing pictures before in the gaming press and the whole sci-fi/fantasy feel interested me.
Then I started playing the game (it was a loan from my friend, there was no drm at the time, kids!). First compared to Outcast's fields, mountains, city, etc., the big city of Omikron just felt empty. Sure you had people wandering around but you couldn't talk to them, ask them for directions, they did not seem to follow their daily routines but simply walk around. The game, like many others, tried to paint a living breathing world but failed and as I said before many games still fail at that today while a few, like Outcast in its time, managed to do it.
Then there was the combat... It was a stark contrast: Omikron made you enter some very bad 3D combat sequence or even worse FPS mode while in Outcast action and adventure were blended seamlessly. It was even worse for me that the invert mouse option did not work (yes, I am one of the few who needs to play with the mouse inverted).
And I got a lot of other quibbles like the save system (console like, you need to find rings in limited supply and you can only use them at save points), clunky controls, the fact that each time you got a new body you needed to train again to raise your combat skill, inventory management was a pain, etc.
Hell, even graphics and musics did not compare. As said before Outcast uses software but has a lot of special effects that you did not see until pixel shaders started to become the norm.
So yeah, after experiencing Outcast and its roaming freedom, Omikron just felt constrained and clunky. Plus the story, which started good because of the mystery, started to unravel along the way.
Omikron was a big disapointment, I wanted to like it, I still forced myself to finish it but by the end I was glas it was over and never tried to play it again. Lots of potential wasted if you asked me. Outcast on the other hand left me a lasting impression, even if I did not realise it until now I unconsciously compared many games to it.