You're right that the different difficulties is implemented in quite a lazy way - usually with just boosting the attack and health of your enemies, and vice versa for yourself. The hardest difficulty is often something like only having one HP. The next level is having more enemies spawn, but it often doesn't go further than that.
As far as fighting in hack-and-slash games are concerned, I find the Onimusha series more interesting (you're a samurai in feudal Japan fighting demons). That's partly because they have the "issen" (critical strike) attack which is triggered either by blocking the attack of the enemy at the last second and countering (relatively easy to learn) or attacking (countering) the enemy at the last split second before his attack lands ("real" issen, more difficult more risky and does more damage). You also have the ability to chain issens by pressing the attack button at the exact time the first issen stops. This is pretty hard to do in Onimusha 3 (too easy in Onimusha Dawn of Dreams, though), because of the hard timing and maybe partly because the animations of the issens can take different amounts of time to complete. (The issen attack has been in the game since instalment one. But curiously the manual said nothing about issens, which meant that I got very confused when all of the sudden I got lucky and one-shot one of my enemies by cleaving them in half.
Issen will one-shot grunt enemies and do a lot of damage to other enemies, and give you more souls (similar to orbs in God of War). I found that this gameplay mechanic was very rewarding to learn to master, because it is very effective and it is satisfying to one-shot enemies (or maybe even take down three at a time) with those sleek animations. By contrast, God of War is much more, like you say, about button mashing since which combo you choose doesn't matter so much (it's mostly about whether you have time for the heavy attaks and if you want to do area of effect damage or single damage). When it comes to difficulty settings, one of the settings in Onimusha 3 involves playing through the game where the only damage that the enemies can suffer are through issens.
As far as fighting in hack-and-slash games are concerned, I find the Onimusha series more interesting (you're a samurai in feudal Japan fighting demons). That's partly because they have the "issen" (critical strike) attack which is triggered either by blocking the attack of the enemy at the last second and countering (relatively easy to learn) or attacking (countering) the enemy at the last split second before his attack lands ("real" issen, more difficult more risky and does more damage). You also have the ability to chain issens by pressing the attack button at the exact time the first issen stops. This is pretty hard to do in Onimusha 3 (too easy in Onimusha Dawn of Dreams, though), because of the hard timing and maybe partly because the animations of the issens can take different amounts of time to complete. (The issen attack has been in the game since instalment one. But curiously the manual said nothing about issens, which meant that I got very confused when all of the sudden I got lucky and one-shot one of my enemies by cleaving them in half.
Issen will one-shot grunt enemies and do a lot of damage to other enemies, and give you more souls (similar to orbs in God of War). I found that this gameplay mechanic was very rewarding to learn to master, because it is very effective and it is satisfying to one-shot enemies (or maybe even take down three at a time) with those sleek animations. By contrast, God of War is much more, like you say, about button mashing since which combo you choose doesn't matter so much (it's mostly about whether you have time for the heavy attaks and if you want to do area of effect damage or single damage). When it comes to difficulty settings, one of the settings in Onimusha 3 involves playing through the game where the only damage that the enemies can suffer are through issens.
They are not hard games to beat, though.