As taken from my blog post on the Bomberman Wiki: (warning: wall of text)

I was thinking about the boss battles in the Bomberman games the other day. Often times I found them very difficult and sometimes either had to cheat to defeat a boss or just surrender. I realized that the Bomberman series has some very difficult boss fights because of similar trends.
The ability to use a bomb is strong indeed. To be able to hone explosions and use them against your rivals is a formidable power. However the developers have taken note of that and work around it to give you a challenge.

For starters most bosses have a high number of hit points and they usually increase with each boss further into the game. The bosses are quite tough to be able to withstand so many direct hits from an explosion before going down.

Next some bosses have advantages that make the timing of your bombs even more crucial. Take [[Eagle Bomber]] for example. He can fly and only when he is in range and low enough to be struck can you throw your bomb. While some bosses can fly and make it easier for them to dodge your attack, others may walk rapidly which not only acts as a defense but as an offense maneuver because of touch damage.

The biggest factor in a boss fight's difficulty is your own weapon's lethality. This may be the only game series I know of where you must dodge the enemies attacks as well as your own! You can have the upper hand in the fight and be well on your way to victory when one misstep can cause you to walk into your own explosion and kill yourself. It takes a great deal of skill to navigate between your explosions and your rivals.

One of the more overlooked factors is the size of the playing field. Excluding certain games you mainly play on a grid-like field that is sometimes limited by the size of your opponent. It's almost like a game of chess the way you must maneuver Bomberman to dodge the lasers, bombs, and whatever else the boss is sending your way. It takes a lot of precision to keep him alive while leading an offense and considering he usually has one point in many of his games, it really puts the player in a pinch. That's like trying to play chess with only the king and trying to defeat the entire army on the other side of the board.

So to sum it all up, the boss battles of Bomberman are quite challenging for reasons that are often overlooked. If it's not the advantages of the boss like their high HP or their ability to fly, it's the ability to navigate on a small grid to avoid your enemy's and your own attacks. So next time you're in a pinch against a boss, just remember the game was designed to test your abilities to their best.