Das Schwarze Auge
I played a one-shot demo of the English version of The Dark Eye about a year ago and it was only similar to D&D in that it was fantasy and used 20-siders for task resolution, but was not a d20 mechanic.
The game had a lot of skills and anytime you wanted to accomplish something you would roll 2-3 20-siders against the relevant skill/trait. I think you needed to roll under the numbers, but the details are hazy.
We only got involved in one combat and I want to say it used an opposed roll mechanic, again, using multiple d20s tied to your martial skill, defense, armor, etc. The combat we got involved in took a long time to resolve because there were many blocked/parried/absorbed blows.
It was a neat game, but very different in approach than D&D. There was also a bit of "strategy" involved in how you chose skills to use for the dice mechanic...or at least that's how it seemed to me.
In the end, I decided it was too complicated/different for my tastes but you might like it.