But probably nothing much else. The chances are high that Mars looked very much like the earth some 3 billion years ago.

But Mars is only half the size of earth. And it's interior would have cooled faster. The earth's interior has remained hot longer than it would have otherwise, but the earth was hit by a Mars-sized planet late in the formation of the solar system. This turned the earth back into a molten world, and the remnants of that collision formed our moon.

A molten interior is important, as this is what produces our magnetosphere. Without it, the solar wind from the sun would strip earth of it's atmosphere, and then our oceans. Mars, at some point, had one too, but no longer.  

So that's probably what happened to Mars. It used to support life. Now it doesn't. Yes, things do change.

You think God regrets creating us by now?

Not only was there life on Mars, there still is. There are military bases that are occupied to this day. The planet was nicknamed The Red Planet as a cover. While there are deserts that are red (actually orange) in appearance due to the high content of iron oxide, but the entire planet is not red. The Martian sky is not red either. NASA uses a red filter to give it that appearance. The Martian sky is actually blue. Yes, blue.
Here's another shocker. There is enough atmosphere (oxygen) to breath although with some difficulty. There is also plant life.