jeeze...and my copies aren't only complete, they're sealed..
the first three games are really, really good.
4 is not.4 takes some of the best aspects of 3 - Style changes and the Add function and removes them, and replaces them with the cool, but limited usefulness of Soul Unisons coupled with being locked to fewer chips, and in my opinion, most of the MN4 chips suck.
I forced myself to play through 4 recently all the way to the ending (once, anyway..I'm not going to do the Ghost 'n Goblins thing of beating it twice to see the true ending). Battle Network 4 can be summed up as: in a simple formula:
1. Reach a new area and explore - both real world and internet area.
2. Be given a task and go on a fetch quest.
3. Have so much text that wasn't screened that there will be a typo in about one out of every 10 lines. Seriously.
3. Tournament battle
4. Plot exposition
5. Boss Battle Network (what makes Battle Network games fun)
6. Repeat steps 1-5.
Some elements of the game are really great and even the typos are charming in how obvious and bad they are, but the frequency of fetch quests drove me insane. I'm not kidding at all. The game has you go on a fetch quest to participate in a tournament battle. Then when you are entered, you go on a fetch quest to learn who your first opponent is. Then you fight that oponent in the tournament. You win, and then the game will show you who your next opponent is, and then force you to go on a fetch quest before you can fight the next opponent. The fetch quests NEVER STOP!
The last game in the series, Battle Network 6 also has plenty of fetch quests, but they are varied and interesting, and far less numerous.
I'd say if you are a fan of the first two games, play 3 next and then skip right to 6. I haven't played 5 yet to give any real opinions on it, but only play 4 if you're super hardcore into Megaman AND extremely forgiving.