Look okay, back in the day "devices" (computers) weren't as powerful, available or cheap. People had a lot of imagination and willingness. They played board games and read books. Then as computers became a thing, they turned these into computer games.
Some "nerdy" games focused on telling a story, giving you as player some choices within said story and all this was surrounded by game mechanics whom as far as I know were stats-based. These were imo RPG, these were based off both a game and a book.
Between now and then machines improved and thus graphics / size / content scale with that. The problem that I personally see nowadays tho, is that game devs - who are sponsored by the men in gray suits above 'em - are pulling a cult-level entity such as RPG into the mainstream. Yes I know, blabla, all this crap about mainstream this, mainstream that.
Sadly it's true, what a lot of people say (even tho some arguements are badly flawed and the hater train has probably more parrots & idiots than actual people voicing their own opinion properly in an intelligent manner) about F4 being a "bad" RPG.
The hater train is mostly flat BS however there are some things that are correct.
What people miss is that indeed, there is no single, easy to set parameter to decide if a game is RPG or not. Games in general can take RPG elements inorder to make both gameplay and story more interesting. The problem is that when a game was already intended to be RPG that the dev takes away from that. Like what happened to F4. Honestly, you have to admit that F4 has some good improvements yet instead of adding them to the game, they replaced old good stuff with these. Which is showing total incompetence of understanding RPG fans and RPG mechanics as a whole. This iis the true reason, people are tilting over F4. They are imo, angry cause something was lost, not because F4 is "bad". Cause it is not bad. It's just not as deep as even F3 RPG wise.
Whoever is responsible for that, be it the gray suits or not, are the problem. Fundamentally you don't need a RPG to look incredible good and invest all your money in that blingbling, you do need to invest all your money in the story and having the story root into different parts. F:NV did this, went the full damn way and it was good (investing in story), F3 did it for the most part but didn't go full RPG. The evidence is there that you literally still have BOS in F4 while you could blow up the BOS in F3.
Both are fun games. You can't tell F3 was bad, it was just not as deep and still.. it is a RPG. Just like F4, you can't say it is a bad game, it's just not the same type as F:NV is.
If you really need more explanation on what "good" RPG's contain then here we go:
1) A very well written and defined story, in which you as a player get absorbed and "feel" like you are the character you play.
---> It is not necessary to be able to graphically modify a pc fully but sometimes it adds (dragon age). However if the story is top level, it isn't needed (witcher, final fantasy, deus ex).
2) Classic RPG leveling system often based on stats. Focused on character progression (game mechanically) this also further down the line goes in sync with the story. If not directly then indirectly one will feel "maturing" of a pc.
3) A world/universe around you that feels it gives you story on it's own, making you want to explore more of it. Aswell as making it so that there are limitations in a logical sense.
Okay so notice how actually all 3 aspects in a way amplify eachother if you think about games that score good an all these points? All this is based off good writing and hard work. When a game FEELS good that is what you get. And when a game LOOKS good you're talking about graphics. You should have better graphics every "gen" but the writing should stay at a top level where all points stay valid. And that is where it goes wrong nowadays.
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To me for F4 in particular;
1) The story started off very good but towards the end there was no big difference in choices. This is caused by key characters not having enough screen time, not being fleshed out enough. Factions just not being established enough in their actual goals. And aswell as post-game there just isn't a damn difference in who "wins" reward-wise, which is a mistake since the game was intended to be played post-MQ.
2) The leveling in F3 made you too OP, in F:NV it was just good. In F4 they should've done a F:NV with improvements. Instead since the release of Skyrim, BGS fantastically f***d that part of RPG up on a grand scale. I have no freaking clue who, what and why they did this to Skyrim and F4 but "perks" are completenonsense.
Good RPG always been with a basis and expanding upwards in a certain fashion. From bottom to top you'll define your pc by taking some skills and postponing others. This is how it's always been. There is no basis at all in F4, there literally is no reason to have any stats known as "SPECIAL". It literally is just there to unlock perks in a linair fashion, once unlocked only your pc level determines how deep you can invest in said unlocked "perk". SPECIAL itself modfies about nothing compared to a good RPG.
"But lol you mentioned deus ex earlier, you don't have those stats modifying anything either in that game". Well now Deus Ex: Human Revolution had fleshed out levels that legit made you build your character in such a way fitting to your personal playstyle. You solve your problems with your talent points there. In F4 there basically is no "level design".. there are just places to talk, stab or shoot people. While this type of approach is fine, your skill trees should still be a vibrant part of your way of dealing with stuff in situations thrown at you. You should be able to talk as a high STR guy in a way a high INT or high CHR guy does not, in dialogue. In no dialogue you should have a different way of handling locked stuff. F4 just doesn't even try to do that. It's non-existant.
3) The world is the same you loved in all previous installments. However it feels that there is little progression in said world both pre- & post-MQ considering you can literally destroy whole factions and their leadership. Also there have been details weirding me out entirely between pc actions in F3 that don't flow through in F4.
But on the good side of the game, it is still a very fun game to explore in. They took a lot of fun stuff from previous games and used it. Infact I seriously hope they keep doing these improvements. The raider logs for example made for entertaining reads and added some life to raiders. There were some fun side stories and added lore, while the only real gripe in this compartment is that it's 2015 and the map feels way too small (as in both too small dungeons and too few AND the map itself is physically too small for the amount already in place lol).
So in a nutshell:
Basically it's going to the bakery for blueberry pie every year because you like eating it for your birthday, okay. But for some reason the pies seem to lack more and more in flavor each year passing. However the pie still looks good and looks visually pleasing and each year small visual adjustments are made. But damn it, it's never gonna be as good as that simple spot on pie from the very first time.