So when you say your game is "as big as Skyrim", do you mean the game world is the same size, or does Caveman have as much content in it for the player to do as Skyrim does?
the game world is 2500x2500 miles in size, and you can walk all the way across it (barring any oceans in the way). you can build rafts and sail across the oceans. and NO LOADSCREENS! all assets are loaded at program start (about 10-20 seconds load time). walk speed is about 4mph. the game runs in realtime (but has accelerated time too!). you have to sleep in caveman, like in the sims, but we'll ignore that for now. so if you walked across the caveman world in reatime without sleeping it would take you 625 hours of real time (26+ days).
I believe Daggerfall is the largest commercial RPG ever produced (It would take real life weeks for a character to run from one side of the world to the other - they tested it).
Good point. running speed in Caveman is twice walking speed - so, again ignoring the need to sleep, we're at 13+ days (2+ real life weeks @ 24 hours a day) to RUN across the world without using accelerated time, cross country travel, or the teleport playtesting cheat. if you used sprinting in Caveman when not fatigued, it might speed that up a little.
the game world contains 60,000 caves, which can be unoccupied, or occupied by animals or cavemen.
it contains 5000 rockshelters - which are similar to caves, but only found along cliffs.
it contains 18,000 huts, which are occupied by cavemen.
it contains 20,000 caverns, which are the equivalent of a dungeon level, or a doom level, or a cave level in skyrim. caverns are generated when you enter them the first time, and saved when you leave. when you return, they are reloaded. caverns repopulate over time.
a new world is generated each time you start a new game - so its random, not hard coded content like skyrim. the entire world is saved when you save a game, so its persistent. and you can build and demolish structures, etc, so its modifiable.
the game also models changes in terrain and occupants of shelters. so berries and fruit come and go with the seasons, vegetation coverage can change over time as the climate changes. cave and rock shelters can change occupants from time to time. new huts can spring up, old huts can be abandoned, as the cavemen move on to greener pastures.
so thats how big the world is.
how it stacks up in other respects:
the game has more than the average number of weapon types - 65 types of weapons - and none are made up. this is partly due to the fact that any tool that can be used as a weapon is considered both a tool and a weapon.
there's no magic in the game, so comparisons in that category can't really be done. the closest thing to magic in caveman is high quality objects, god artifacts, an god effects.
the game includes objects and armor, but in numbers typical for such games (300+, and ~30? respectively).
caveman has over 50 types of "monsters" - so far.
there are no classes, instead there are skills, 48 or so of them. only 5 or so are weapon skills.
you can cook over 30 types of food, and yes there's a cooking skill. since its a person sim, like the SIMS, food is required, unlike skyrim, where its just a weak powerup in a shooter game.
but the place where caveman is REALLY big, is in the actions. like the sims, you can select things and interact with them. i've never calculated the total number of actions in the game since its so large. i know its over 1000, perhaps as high as 10,000 or more. it has over 100 generic action class handlers, each of which handles an entire class of actions (all repair actions, all cooking actions, etc).
by comparison, in skyrim you can open a container, sleep in a bed, open a door, sit, use smelter, use forge, use grindstone, use armor table, use alchemy lab, use arcane enchanter, pull chain / throw lever, and cook. did i forget any? of course this is not a fair comparison, as skyrim is a quest based rpg shooter with some interactive/open world elements, not a person sim.
open world play is another "big" feature of caveman. there are quests, but they are optional. unlike skyrim, the game is primarily about open world play (think original table top D&D role playing, caveman style), not primarily about completing quests. when i evaluated skyrim, open world play was the first thing i evaluated. i found it to be not-so-great. again, not a fair comparision, as skyrim is designed to be an immersive quest based shooter, and caveman is an open world rpg / person sim.
and then there's replayability. Caveman is designed for maximum randomness. nothing is hard coded, everything possible is random. The whole idea is it should be random enough that even i as developer can play and enjoy it without knowing what will happen next in the game. so everything is randomly generated at game start or when you first encounter it (IE cavern level maps). the game does not use hard coded spawn points, except for occupied caves and shelters. all other encounters and events are random.
by contrast, skyrim is entirely hardcoded, same map, same dungeons, same quests, same NPCs - every time you start a new game. while evaluating it, i created new charcters to test each thing. so i made a fighter for open world play, a dragon slayer, an imperial, a mage, a stormclock, etc. by the time i was done evaluating it for work, there was little game left for me to enjoy as a fan of the elder scrolls!