Topic: Super Mario vs Super Mario Bros.

Yes we all love Mario games. But I ask this: What happened to the Bros? During the 3D revolution, two-player Mario games became a thing of the past, to be replaced by one-player games. I loved sharing the experience with a friend, and I loved playing as the Great Luigi. So here's what I think makes a game a "Bros. game":
1. Obviously, Luigi must be in the game. but not as an NPC, we must PLAY as Luigi.
2. Multiplayer mode, after all, doesn't having a Bro mean you need another player? You know, "You be Mario, I'm Luigi!"

Game Breakdown:
Mario Bros, SMB, SMB3 all are obviously Bros. games
SMB2: Luigi-check. but no multiplayer? not directly, but we used to just pass around the controller anyway, so it's a Bros too!
SMW: Luigi-check. 2P-check. but no Bros in the title? Well originally it was SMB4, they just changed the title to make the game sound bigger and better for the new SNES. So, yeah it's a Bros game too!
SMW2: Ok Yoshi's Island is hardly a Mario game at all, and it's still a great game, but not a Bros!
SM64: No Luigi, No 2P! So no Bros! Too bad too, cuz originally Luigi was going to be in it and have a 2P mode. I would have loved it even more, but alas, SMB64 it is not.
Sunshine: No Luigi at all, No 2P! So no Bros!
Galaxy: Luigi is unlockable, and there IS a 2P mode, but 2P is not Luigi. Though I love this game, it's just not Bros!
New SMB: Yes! a New Bros game at last. and such a clever name too (not). While the 2P mode is limited to the Mario vs Luigi mode because it's on a portable, it meets all the requirements. I call it SMB5 myself. cuz it is. so there.
What about the Mario & Luigi RPG series? No 2P, no Bros!
Galaxy 2 will probably be like the first Galaxy in this regard, but I guess we'll see...
and New SMB Wii? Definitely a Bros game! I can't wait! Ima gonna call it SMB6 and you can't stop me.

Do the Brawls count?

I think your reasoning on why Yoshi's Island is a bros. game is pretty stupid. There is no multiplayer mode, plus, there is no Luigi in the game, besides the opening cut scene or maybe the end when you save him. I'm not saying it's a bad game, I'm saying it should be a non bros. game, even though it says Super Mario World 2 above it.

Whoa there wii man! I never said Yoshi's Island was a Bros game, cuz it's not. I was just saying it was barely even a Mario game. In fact, It originally wasn't even called SMW2, they just added the pretitle to link it to the most popular SMW. The original title was Super Mario Yoshi Island. Definitely not a Bros game! I have edited my original post to clarify.
Oh and Golgo, assuming you are referring to the Smash Bros Series, then obviously the answer is: it's a spin-off series.

oh. sorry I was so hard on you. but the reason I thought you said it was a bros. game is because you didn't say whether it was or not, and you just praised the game.