An addictive, entertaining, and satisfying experience.
First things first, I'd like to take the time to explain why it's not for everyone. This game requires a lot of thought and preparation. One of the aspects of the game is that you can gather materials from various plants, mushrooms, mining "hotspots", catch insects, etc, etc...all of this is so that you can make new equipment and tools to take on hunts. You can usually do this as you're hunting, but if you don't have the patience to go around to various areas and gather things that you need, you're going to get tired of the game real fast. That, or you'll go broke from buying everything at the store.
Regardless, here's the breakdown of the good and bad of the game...starting with the negative points.
The Bad:
First of all, let me start off by saying that the online play is great. It's one of the strongest features of the game. But there's just a few hitches that strike me as odd. First of all, it would seem there are some monsters that appear for you, but no one else. This is evidenced by your allies, who will occasionally attack thin air, then proceed to gather from an invisible corpse. This is a minor thing (there's never a large/tough enemy that only appears for one person), but from a game with strong cosmetics otherwise, it seemed silly. Perhaps a necessity due to the Wii's hardware capabilities, but nonetheless, it's worth a mention. Also, there can be lag at times, and the monsters can sort of jump around, which can be annoying in crucial moments of a fight.
Finally, the offline play is somewhat lackluster in comparison to the online. It's still enjoyable, but I found myself going back to play online over and over because I liked the community and ability to hunt with others. The only complaint I have is that you cannot grow crops or send out fishing expeditions in the online mode, while you can in single player. It seems to me that these options should be available in both, but that's just my opinion. Still, you can always hop into single player mode to farm a few things, pick up crops, sell crops, etc. and then jump back into multiplayer.
The Questionable:
Perhaps the biggest hit and miss in Monster Hunter is the battle system. First of all, there are various attacks and combos for every weapon, and knowing when and where to use them is essential...because if you don't, you'll be left wide open. Attacks take time, especially with weapons like the greatsword. If you don't choose your attacks carefully, you'll be quickly tossed aside by most monsters, and probably won't do well overall. Also, items and tools take time to deploy/use. While a potion can be used almost instantly, sharpening your weapon (which dulls over time after attacking with it) or setting a trap can take planning, and usually some help from your allies to act as a distraction. I find these things to be a plus, as it adds strategy to the battles. If you prefer hack & slash, you might want to look elsewhere (though, you still could give it a try).
The Good:
This game has plenty of things in it that are amazing. First of all, the visuals are fantastic. For a Wii game, it has amazing detail in the creatures and the scenery. Second, you get huge satisfaction out of taking down the larger creatures that you can wrestle with for half an hour or more, and then finally getting your rewards. The creatures themselves are a huge plus to the game...each has its own unique habits, habitats, and methods of attack. They behave fairly realistically as well, and a lot of them will do some rather surprising things that will keep you on your toes the first few times you fight them. But most of all, there's just a lot of depth to the game...from deciding what equipment to bring to the damage calculations based on how you hit with your weapon.
The game is also highly addictive, and will have you coming back time and time again to complete that set of armor, or upgrade that weapon. But those things aside, the main fun in the game really does lie with the thrill of the hunt - battling unique creatures, tracking them, and reaping the rewards. There's also a number of various other quests as well to mix it up a little bit and keep things interesting.
I guess that's it. It's one of those things you'll have to play to fully appreciate, really, but it's well worth the time, effort, and money.