First of all, the notion that all the enemies are entirely one dimensional and the various actions are equivalent to just fighting isn't true. While that might be the case for a portion of the enemies (and admittedly the start is bad for this because they're all simple enemies because it's a tutorial) there are examples of rather complex encounters as early as before reaching the first town. The 'Greater Dog' enemy has a large number of ways to interact with him and end the battle, like ignoring him until he becomes bored and leaves, or making him get too excited and pass out, etc. These do all just play out for gags as opposed to tangible rewards, but it's certainly much more interesting than the descriptions of 'frogs shoot flies and thats all' that people have been giving as examples of the combat.
Here's a list of all the flavour text just from this one particular enemy:
Flavor Text
- It's so excited that it thinks fighting is just play. [Check]
- It's the Greater Dog. [Encounter]
- Greater Dog is seeking affection. [Neutral]
- Greater Dog is waiting for your command. [Neutral]
- Greater Dog is watching you intently. [Neutral]
- Greater Dog is not excited enough to play with. [Play]
- You call the Greater Dog. It bounds toward you, flecking slobber into your face. [Beckon]
- Greater Dog's ears perk up. Nothing else happens. [Beckon again]
- Greater Dog curls up in your lap as it is pet by you. It gets so comfortable it falls asleep... Zzzzz... ... Then it wakes up! It's so excited! [Pet after Beckon or Ignore]
- Greater Dog's excitement is creating a power field that prevents petting. [Pet again]
- You make a snowball and throw it for the dog to fetch. It splats on the ground. Greater Dog picks up all the snow in the area and brings it to you. Now dog is very tired... It rests its head on you... [Play after Pet]
- As you pet the dog, it sinks its entire weight into you... Your movements slow. But, you still haven't pet enough...! [Pet after Play]
- You pet decisively. Pet capacity reaches 100 percent. The dog flops over with its legs hanging in the air. [Pet #2 after Play]
- Tummy rubs are forbidden. [Pet again]
- Greater Dog is too tired to play. [Play again]
- Greater Dog inches closer. [Ignore]
- Greater Dog is making puppy-dog eyes. [Ignore 3 times]
- Greater Dog decides you are too boring. [Ignore 4+ times]
- Greater Dog is patting the ground with its front paws. [Neutral after petting]
- Greater Dog wants some TLC. [Neutral after playing]
- Pet capacity is 40-percent. [Neutral after petting again]
- Greater Dog just wants affection. [Neutral after ignoring]
- Greater Dog is contented. [Neutral after meeting spare conditions]
- You threw the stick and the dog ran to get it. You played fetch for a while. [Use Stick]
- Greater Dog is panting slowly. [Low HP]
It is rather facetious to have all that available to you and then claim that there was nothing distinguishing it from the frogs.
Outside of combat, even in the tutorial portion of the game before you've left the ruins, there are things like the way the candy pillar reacts if you take more than one piece, or Flowy creepily being behind you that you can notice before he burrows away if you backtrack in many places. The game also reacts to subtle things like whether or not you were injured before reaching the house, or if you kill the frogs in the random encounters, they won't be waiting further along in the ruins to give you advice. There's like half a dozen extra pieces of dialogue written just in case you were curious enough to find out what happens if you just sit and wait for Toriel to come back after she tells you to wait for her while she runs her errand. The game is utterly crammed with details like these that most of the detractors seemed to have not noticed at all.
Comparing this to something like Skyrim where you can shove buckets on people's heads without provoking a reaction is it that hard to see why players would be enamoured with a game that actually responds to things they do?