Do you have the XApp Status applet on your panel? If not, adding it will make some icons look more or less ok. Although it sometimes just displays duplicates of these icons, so there's that.
Other than that, I don't think there's a way to make all icons the same size
For some time, I considered Orbiter to be better at providing an arcade experience of "choose ship/scenario and fly away". But now that KSP also has scenarios, maybe this argument doesn't really stand now. But I still think that Orbiter's MFDs are better than KSP's manoeuvre planner (at least for precise manoeuvres)
Beacon Pines -- a charming mystery story with anthropomorphic animals. Has an interesting take on the visual novel formula by having you unlock new dialogue choices as you progress through the story; that way, you naturally explore different paths the story might take. Night in the Woods and (possibly) OneShot fans might like this one.
Oolite -- a solid FOSS remake of 1984's Elite. Has a bunch of mods for it; some expand the gameplay quite substantially.
Orbiter Space Flight Simulator -- imagine a Microsoft Flight Simulator game, but you're going to space instead. Or Kerbal Space Program, but without the rocket building mechanic. That being said, KSP fans (and fans of space in general) should enjoy it.
Transcendence -- Star Control II meets Rogue. A cult classic in the space sim genre that's been in development since 1995. Space dogfighting, trading, mining, smuggling etc, but also traditional roguelike stuff like unlabeled barrels and containers (= undiscovered potions) and permadeath (optional). Highly moddable, uses XML as the modding language. Has a free version (see link) and a Steam release, which includes the paid expansions.
Just recently started Lunacid, and I'm having a blast. I'm a fan of dungeon synth and its subgenres, and I"ve been looking for a game that has those vibes for quite some time. This one seems to fit the bill quite a bit. And I also have wanted to check out King's Field, but was afraid that it might be too dated to be enjoyable; Lunacid seems like a fresh take on that dungeon crawler style of gameplay. The only thing the game lacks imo is a dedicated pause button
Oh, I really love Hacknet! Played the main game and the DLC. Discovered it one day while browsing Rémi Gallego's (aka The Algorithm) discography, and found out that he did some tracks for the OST
I mean, you can put the applet on the panel yourself, if you want to