Strictly speaking, SaGa 2 actually had this sort of growth system for its Humans and Espers, though you only had stats and not skills. Of course, SaGa 3 changed to a more conventional XP system (though the DS remake changed the growth system to something more SaGa-like, throwing out XP growth).

SaGa Frontier is also interesting, where Mystics get stats from absorbed monsters (but can have at most 3 absorbed at once) and Monsters absorb skills from enemy monsters and change forms based on known skills.

SaGa 2 and SaGa Frontier have Robots/Mechs whose stats are solely based on equipment. To make things more interesting, they don't have the usual body slot limitations; nothing prevents you from giving a Robot 2 suits of armor and 3 helmets to wear at the same time. (This is actually a bit of a game breaker in SaGa Frontier, where a Mech with the right equipment can have 99 defense in all categories.)

Do you have any simple tips on how to get along with the game? So far I've failed to play through it even the second time I tried, despite checking some guides and paying close attention to affinities, but maybe I did the exact thing that you say would leave you underpowered and concentrated on enemy types (e.g. dragon)? I remember that fighting most regular opponents was no problem, but many of the boss fights were a real pain, with my character doing next to no damage to them - even the dragon types although I had a good dragon affinity weapon. And then at some point these boss fights happened much too often for my taste, like I only just barely defeated the last one with much frustration and tedium and there's another near invincible thing right around the corner. That's when the game lost me, although I was really intrigued by setting, story and general gameplay. :(

I actually never did a FF2 playthrough without abusing this mechanic and leveling me in the first 2-3h to the point I can just roflstomp through the rest of the game. Kinda took something away I think, but I could never resist it.

Disgaeas system isn't overly complex or really new, but the way they put level grinding to 11, or rather to 9999+186000, is something I really like about the series. In addition to leveling items, weapon/skill levels and more. Not many games have a post game that big and it can give you the feeling of having raised someone this powerful.

Here are a couple from games most people wouldn't consider RPGs:

Castlevania: You can level up your whip twice by collecting power ups that drop from candles. The first requires you to have 4 hearts before it can drop (you start each life with 5, which are used up when you use sub-weapons), while the second requires 8. Your sub-weapons can also level up; if you kill enough enemies with the same sub-weapon, you will get a double shot, which allows you to have two shots on the screen at once, and there is also a triple shot. Note that picking up another sub-weapon will cause you to lose the one you had along with any double/triple shot you might have had. Dying causes you to lose your sub-weapon and sets your whip back to its basic level.

Gradius: At the bottom of the screen, there are some blue boxes. Some enemies, when killed, drop power-up items. The first one you collect will highlight the first box, while the second will move the highlight to the second one, and so on. By pressing a certain button, you can get the power-up indicated on the highlighted box, and the highlight will disappear. (Note that you might not want to get the speed power-ups; too much speed makes your ship hard to control, and the entire game is an auto-scroller outside of boss fights, so it won't help you beat the game faster.) When you die, you lose all your power ups (I consider this to be a major flaw in the game; the punishment for death is so bad it is typically not worth continuing once you die.)

Interesting. I think I want to reconsider to include them in my wishlist here.

Anyway, a game with good leveling system... Hmm. FF VII ? there is a point in the middle of the game where you could just grind away the enemies that gives much ex and become strong earlier.

Okay I'll ask you; have you had the drop in FPS when you zoom out with Sacred 1?

Sorry, I didn't.
Or I at least can't remember any noticalble slowdonws and when I last played Sacred 1, I didn't even know what FPS means. And even nowadays I don't care as long as it's not a fighting game, shmup, or <30. How low did it fall?

Undertale...

It's notorious for slowing way down when you zoom out. Of course you really only need to zoom out when you are using a ranged character so anyone in love with the Vampire or Gladiator would never notice. There are several things on the web about it but they are either no help or several years old.

I know that I played it zoomed out, but I really can't remember any slowdowns. Though I know it had some issue on newer machines for which I had to run it on one Core only. But I think that was multiplayer related.

Omnimusha actually level up your weapons & armor with souls. And you have health and mana souls to suck in addition to red soul.

Vampire Bloodlines gives no exp by defeating enemies, only by completing quest. And you do not level up nor grew stronger, only boosting your skills. That system should give the devs less problem balancing.

You're supposed to chain timed attacks on bosses to do damage.

IIRC, each attack after the first does a percentage of the total damage in the chain up to that point, and it accumulates extremely quickly after a certain number of hits in a row.

If you did a lot of damage with the first hit, it would be way way too easy to kill bosses with one chain unless they massively bloated up boss hp.

It's also probably more efficient to worry about attack type weaknesses and elemental weaknesses instead of grinding out affinity towards that enemy type.

(and there's also some other strategies such as using Phantom Pain)

But I seem to recall that I did next to no damage at all with the first hit (I think even literally zero), so I had to chain attacks like crazy and get the risk up very high, just to do *any* damage, and it was still pretty low, and that way it took a lot of time to defeat the bosses and it wasn't much fun ... Is that how it's meant to be or an indication that I did something wrong?

This is the second time I'm recommending this game in like a minute.
But there's always Path of Exile! It is a Hack and Slash RPG with a leveling system similar to that of Final Fantasy 10 with the sphere grid. All of the classes start on different parts of the grid with different nodes corresponding to the class. But on later levels any class can go anywhere, which enables a huge build diversity.