Nobody managed to get even remotely close to what Frontier has achieved. Walking on planets - FDL recently announced that Elite 4 will feature the possibility to get out of your ship and walk on the planet's surface. This certainly is something in new in the history of space sims. This point seems to be something of a mystery. The flight engine will be more like Elite - This point caused a small war on alt.fan.elite.
Some people prefer the Elite flight engine, other prefer the Newtonian flight engine.
The Newtonian flight model is more like what you would observe in real space. In order to change courses, the ship has to use its engines to propel itself onto the new heading. It's hard to find a game that would properly show this. The flight engine in Elite is similar to the one that most space games use. After you turn the engine off in mid flight, the ship will start to slow down.