While Monster Hunter 3 Ultimate is no slouch when it comes to content, the game certainly isn't for everyone. I admit that before Ultimate, I too had a slight aversion to the series. I've played the PSP entries and even Tri on the Wii, and I wasn't quite sold on the premise. Of course, it could have been due to my lack of patience more than anything. That said, now that I stuck through Ultimate's introductory series of quests and worked my way up to much harder and more satisfying hunts, I see just how much potential the series has when you immerse yourself in its culture.
Unless you plan to dedicate your time with Monster Hunter, it probably won't be for you. Like an MMO, the goal of Monster Hunter is to constantly advance your character. Though, unlike MMOs where progression is measured in experience points and levels, progression in here is strictly based on the quality of your gear. Your health and stamina bar are mostly affected by various consumables and food, and how much damage you can withstand to how much damage you deal is all based on buying, upgrading and developing new equipment.
There is a near-perfect cycle to every single task in Monster Hunter 3 Ultimate. Taking quests or going out on hunts will allow you to scavenge dead monsters, plants and various ore for upgrade materials. Going on tasks will progress the game, while going out on hunts without missions will allow you to gain resource points to upgrade Moga Village (the game's hub). All the materials gathered can then be combined to make new items that can either enhance your character or equipment, or they can be used to help you with making hunts a tad easier. Your farm can raise plants and insects, a fisherwoman will send a boat to gather fish, and even a cute cat chef will prepare stat-enhancing meals that are sure to help you out during missions. Everything in the game exists for a reason and works together in a brilliant ecosystem.
The plethora of missions already available in Tri is expanded greatly in Ultimate. Not only are there a myriad of quests available to you as you progress through Moga Village, but sailing off to the Port Tanzia and the Tavern will reveal a whole new set of quests that will test your abilities as a hunter. Aside from that, there are also Arena quests that pit you and certain monsters against one another in a small, enclosed space. If you think that there isn't enough to do in Ultimate, you're doing something wrong.