Monster Rancher 4THE GOOD: Monster Rancher 4 evolves from it's predecessors in many ways, and each one of them is an improvement. You can now raise up to five monsters, adventures have been made so they are more involved, your ranch can be customized, graphics have been updated, etc.
THE BAD: Adventures, though vastly improved, are too long. Save points and/or set levels rather than randomly generated ones would be a further improvement.
SUMMARY: I have have followed the MR series for a long time. I own all basic console versions (1,2,3, and 4), as well as the handheld MRA2. While they all had their strongpoints, and were great games at the time (and still are), MR4 completely blows them away. There is an odd level of difficulty balance that actually works out quite well. It may seem easy at first, but it gets more difficult as you go, but only in small amounts...until you hit S class. At that point you are forced to take what knowledge you have gained and actually impliment it rather than continue to coast through the game.
As with all MR games, this one is highly addictive and has infinite replay value. However, you are now much more involved with your monster, and everything you do affects it in different ways. Being a researcher of the game, I have learned that often times there are effects that you can't see. Things are affected more by breed than they ever were before. This game has truly reached a new pinnacle of strategy in the series.
One thing that makes this game even more enjoyable: Online tourneys. More people should know that due to the 2 player AI mode, you can have tournaments. Check out monster-rancher-metropolis.com for details on how to do this. You want the coliseum section.