I have yet to play a space-based game featuring proper scale
Frontier: Elite 2
Frontier: First Encounters
Pioneer (open source remake of sorts of the above, still in the works)
I-War 2.
Marie :
They all feature proper scale and not in the "cube few km across, but at least planets are just background" sense - they feature planetary systems of realistic size, with astronomical objects of realistic size.
The first three also feature orbital movement of 'static' objects (like stars, planets, moons and stations) and simulated gravity so ships can orbit as well, they also feature pretty much full size galaxy (slice of Galaxy in FE2 and FFE so the right dimensions but less stars and flattened) and hand-coded Solar System and a handful of nearby or notable stars. They also allow planetary landings (seamless), so you get both deep space and planetside action.
I-War 2 fares comparatively poorly in that regard - scale of its systems is about right, but it's limited to a handful of them (not that it's any problem) and, more importantly features no gravity or orbital movement despite them being pretty fucking important in actual space where everything buzzes around everything else at kilometers per second. It also features sort of random and ugly backgrounds despite the systems in it being supposedly a small cluster of nearby stars, which means they should mostly share the backdrop of their stellar neighborhood.
In terms of movement, I-War uses exotic drive to propel you across interplanetary or interstellar distances, while the other games have interstellar hyperdrive, but force you to move via conventional means across systems themselves, with time compression allowing to shorten the time in transit from days or even weeks game time to minutes IRL.
Now, "looking good" may be a bit of a problem - both FE2 and FFE are from the nineties, and not late nineties either. They do extremely good job looking good with the means they use, but the means they use are restricted to what could work on 286/Amiga/Atari ST and pre-Pentium era PC respectively.
Another problem may be lack of trade and the quality of action.
I-War 2 generally fares the best in that department - the trading is relatively non-absorbing and boils down to selling what you've looted (because Yarr! and stuff), while the combat is relatively fun and complex affair, with directional shields, subsystem targetting and variety of weapon and other options (like remlinking). On the downside it has autorepair rivalling modern popamole health regen, useless HUD, horrible controls (you can tweak them to the state of usability, but you need to do it by hand, in the .ini), and incredibly stupid AI that can't grasp it's in Newtonian environment (which can be hilarious, if you know how to exploit it) or that missiles are limited in supply so it's better to conserve them than to blow through all of them as soon as the enemy contact is made. I-War 2 is also mission driven although you do free-roam in between missions to collect funds by the means of Yarr! and it's fun.
FE2 and FFE fare worse. You may need to trade a bit or do stuff like delivery work to afford some equipment or bigger ship. Afterwards, however you're pretty much free to do what you want including risky stuff like piracy, bounty hunting, assasinations, high risk deliveries and taxi, even military work (but you'll have to grind those jobs before getting to the interesting ones, alas). You may want to keep trading but it's in no way obligatory.
The combat is mixed bag, subsystem damage is in, but no provisions for subtargetting, weaponry is limited to lasers (which are effectively hitscan) and missiles which are very limited in supply, shields are omnidirectional and you can only carry one laser per direction (front mount, in bigger ships also rear mount, the biggest ones may include turrets). AI is somewaht derpy when it comes to shooting and collision avoidance, but is pretty mean with missiles - it has an uncanny knack for launching them when you have the least chance of doing anything about it. Despite simplicity of combat it may take you a while to master, but won't provide much entertainment afterwards.
The most fun and memorable moments you can have are when something important gets shot off and you have to cope with that (assuming you don't reload, that is) - you won't find this kind of fun in I-War 2.
Pioneer is, as of now, unfinished. Weapons are currently similar to FE2/FFE, but with projectiles replacing lasers, so you actually hitting and avoiding hits is more of an actual gameplay. OTOH subsystem damage is not implemented as of now and there are few opportunities for combat. Combat visuals are also still bare bones - with temporary (ugly) explosions, and poor visibility.
Finally, due to scant opportunities for combat you will have to grind boring stuff for a while before getting opportunity to do something more interesting (usually deliveries, not trading, though - could never be arsed to trade in Pioneer).
On the upside, you get actual, rather than maximum mass/maneuverability trade off and delta-v budgets are stringent enough to also be a factor in how you can gear your ship for particular mission, so there is more gameplay to that than just fitting everything you can fit into the hull.
Will post screenies/vids later.