The probably worst rulesystem I ever encountered was The Elder Scrolls (TES). Especially TES3 Morrowind and TES4 Oblivion, which are the two TES games I played extensively. I tried really hard and really long liking them but in the end I completely failed. These rulesystems have been designed without any care for balance, depth, or variety.

- The game would constantly monitor your every action, increasing your related skills. That in itself weird and not great, but tolerable. Its still the case in Skyrim.
- To level optimally, you had to make sure that every levelup had 2 (or possibly 3) stats that could be increased by 5; 2 if you wanted to also increase the luck stat, which always only could be increased by 1 anyway.
- To be able to increase a stat by 5 you had to train the corresponding skills so they increased by at least 10 in total. There was no skill linked to luck, so luck would only be increased by 1 every levelup. Obviously to get the best character possible you wanted the luck skill at 100, too.
- If you would increase your major and minor skills by a total of 10, you would level up. So you had to increase your selected skills by 10 but before you did that you had to increase the not selected skills by 10 as well, and it had to be skills linked to two attributes. Increasing skills not linked to these two attributes would be highly discouraged, because it would make it much harder to level these attributes later.
- This ironically had the consequence that you would want to pick major and minor skills that you did NOT want to use, at least not for a long time, to level optimally. Ideally your pick of major and minor skills would simply be those that could be controlled the easiest to level.
- The constitution stat which gives hitpoint would not apply them retroactively, so you always had to increase it at the start of the game until it was maxed ASAP. Not sure if even Skyrim fixed that (I havent played Skyrim). The re-release of Oblivion has fixed that.
- Therefore, since Luck was also so hard to raise and always started at 40, your two starting stats would always be Constitution and Luck, or you would weaken yourself in the long term for no good reason.
- In a truely stupid turn of events, Oblivion actively forced you to powergame this system because the power of opponents raised linearily with your character.
- Combat and magic stats would actually improve the power of your character, but thief skills and social skills which didnt had to be increased the exact same way, and would also make you increase in level in the same way. Again this was especially bad in Oblivion where focusing too much on out of combat skills early could make the game completely unplayable, for the opponents leveled strictly with the main character and would get riddiculously hard.
- Some birthsigns gave you a very temporary early buff, others would keep being strong until the endgame. Btw another thing still true in Skyrim. Thats why I always played Atronarch; restoring mana with potions was needed anyway and Atronarch gave you the biggest mana buffer plus mana absorption.
- Races would be the same, with many advantages becoming utterly irrelevant. Breton and High Elf would be immensely more talented at magic than any other race, and there was nothing compareable for combat. Thats why I always played Breton, because the weaknesses of High Elf just sucked too much and Atronarch already gave a huge buff in maximum mana anyway.
- There was nothing in the game that gave any incentive to make anything but a master of everything character. Everything else would be a nerf to yourself for no reason.
- For example if you would play a Redguard or an Orc in typical fighter setup (like: some weapon type, Heavy Armor, Block, Armorer, Restoration for healing, and I think Alteration for locks) you would basically reach maximum powerlevel at 15 or some such and leveling would already be over already, because your fighter stats would be maxed at this point. Yes sure the game would also be completely easy since you are really good at (melee) combat, too; but also very boring.
- So, aside from a few choices like race and birthsign, every character would end up in the same place in the end.
- Also: FRIGGIN MORROWIND CLIFF RACERS *rage*. In the end I got a ring of (permanent) invisibilty (self crafted) so they'd finally leave me alone. Just equip the ring when you get out in the open and reequip whenever you broke invisibility.
- Etc etc etc

Really the best time I had in TES was simply leveling by console and then just enjoying the actual story etc at maxlevel.

TES5 Skyrim finally fixed the worst of these issues. You could increase stats as you wanted, without having to carefully level skills to get the optimal result. And you could pick feats freely from different feat trees, instead of just getting feats for reaching certain skill values. Of course Bethesda screwed this up again and you could get to level 200 something and get all feats in the game, but at least with regular gameplay you would end up with an unique selection of feats for your character.

So Skyrim fixed the issues of balance and variety. It still lacked in depth though. Especially the general flatness and boredom of the magic system still stayed the same as always. Damage damage damage and very few standard tricks like invisibility.

The recent re-release of Oblivion also fixed at least the stupid idea that stats raise by up to 5 times during levelup, which honestly is clearly the worst issue in all pre-Skyrim games. You cant freely choose feats though.