I can easily sum up Megaman Battle Network 2 by saying that if you were a fan of the first one, there's no reason why you won't like the second one because it's generally a continuation. The first one must have exceeded the expectations of Capcom, or else we wouldn't have seen this sequel, or myriad others after it. Many of the basic assets (characters, towns, battle system) are reused... which explains how they could release both games within the same year (in Japan, at least). But Megaman Battle Network 2 isn't the same game. There are indeed some differences.
For starters, I would have expected, in typical Mega Man fashion, for the original antagonist, Dr. Wily, to make a triumphant return for revenge on the citizens of DenCity. Surprisingly, he's nowhere to be found, nor is his organization, the WWW functioning at this point. Instead, we are quick to learn that criminal activity is on the rise on the Net thanks to a new organization known as Gospel. No one is sure who exactly is running this Gospel (whose name, by the way, is a nice harkening to the Japanese name for Bass' robot canine friend... and is pleasantly complemented by the mastermind of the organization using Bass.EXE as his NetNavi companion). We're not even given many clues, aside from meeting him briefly in passing as though he were just another NPC hanging out. Cutscenes with the character's portrait left in shadow tell us nothing. In fact, I don't remember his name actually being mentioned in-game.
One of the biggest changes comes with MegaMan.EXE himself. He's your buddy. He's your go-to NetNavi for advice. He's your e-mail secretary. And indeed, he still performs the same basic functions as a virus buster. Taking on opponents via either instigated or random encounters, MegaMan spars against various types of viruses, each with its own unique attack style, on a 6x3 grid (with 3x3 dedicated to you, and 3x3 to the enemy). MegaMan can either use his buster to take down viruses (the slow method), or he can invoke Battle Chips from operator Lan's active folder to perform special attacks. Such chips are collected throughout the game, similar to a Pokémon-style hunt, but... you keep your findings in a folder, not a Pokéball... To make things slightly more complicated, or to make things slightly more customizable, you can find additional folders to keep chipsets in, and they can be switched whenever you are outside of battle.
Thanks for the pep talk, MegaMan. Appreciate it.
But some things are definitely different. After a certain story point, your battle pedagogy will be more closely analyzed behind the scenes. You won't know it. Nothing will show it. Eventually, MegaMan will inherit a new Style based on how you normally act. By donning a new Style (and a snazzy new look to accompany it), your offensive and defensive power will be modified to suit your needs. Each Style is associated with an element as well, and you'll be better suited to take down enemies of the opposite element. Heat vs. Aqua... Wood vs. Elec... Ryu vs. Blanka... Oh, wait, wrong game.
Perhaps more annoyingly, MegaMan.EXE does NOT recover his health between brawls, unlike the first Battle Network game. This means that recovery-based chips and a defensive stance play a stronger role in your journey. Megaman Battle Network 2 introduces SubChips as well, which can be used to restore health between battles. They do serve other functions, but if you have the reflexes of a bowl of clam chowder, these SubChips could be your saving grace.
Other new additions to the game include a job board that can lead to some nice rewards and the introduction of NetSquares, central hubs within the cyber framework of different parts of the world. But other than simple changes like this, Megaman Battle Network 2 is more or less an extension of its predecessor. As I mentioned before, it recycles a large quantity of graphics, so some places should look very familiar. There are indeed some quaint new areas, such as the rustic Okuden Valley campground and ye olde castle headquarters of the Official NetBattlers in Netopia, each with its own charm. The music has also seen a bit of remixing, although the main town theme is still very similar. As per usual, that electropop soundtrack will keep you kickin' for hours.
The bottom line is that if you liked Megaman Battle Network, then this sequel will not disappoint as it is ultimately more of the same. The game has seen some advancements and tweaks here and there, but it's ultimately the same Lan & MegaMan.EXE combo you have come to know and love. Execute!