Dr. Mario is the game you're looking for. It comes with a 1-4 player co-op mode where people can just grab another remote and hop in and out without needing to change options or even pause. It gets hilarious when 4 people are trying to play at once, in the same jar with the same viruses, and 2 or 3 pills are simultaneously falling really fast. Other than that, the regular Dr. Mario mode is online with friends or strangers. Also, the game is still perfect.

 It is perfect. #2 in my top 5 Wii online games.

1. Mario Kart

2. Dr Mario Wii

3. MOH:Heroes 2

4. Call of Duty :WAW

5. Tetris Party 

LostWinds is AWESOME. My fav. WiiWare game by far.

Edit: crud.  I read the OP again.  You have it.  Well... its awesome. =)

Orbient is a remake of the Japan-only GBA game Orbital, which was part of the amazing Bit Generations series of retro GBA games that sadly never left Japan.  It's good.  I don't know exactly what's new in Orbient, but even if it's a direct port of Orbital, it's gonna be good.

Dr. Mario and Orbient it is I think.

PAL bro reprasent !

Tetris Party is indeed online, there's a tons of mode (even a Wii balance board I didn't tried since I haven't the device), and the 4 player multiplayer is just insane. Good thing is that everyone can play and master it quickly !

Onslaught is a great WW title, especially when you try to unlock the special weapons.

World of goo is good, but I am stuck in the third world atm :/

I recommend you Star soldier R if you are a scorer and if you like shmups

Good choices.
Dr. Mario is better than Tetris, there's challenge in there. Between Orbient and Cubello, I'd go with Orbient too, if I'd want a relaxing game.

No ta... I am not interested in the majority of VC..... I have been dissapointed with 5 of my 9 purchases. (F-Zero, Galaga '90, Sin and Punishment, Sonic 3, Lylat Wars) and only mildy interested in a further 2 (Sonic 1 and Lost Levels) so I only really enjoyed my re-purchase of F-Zero X (I sold my N64 copy ages ago) and Super Mario 64.

If I were to get more VC, it would probably be 1080 snowboarding or Wave race 64.... or perhaps but not very likely, Streets of Rage II or Super Mario Bros 3.

Onslaught is pretty fun in some ways, maybe the biggest problem is, that some levels are way too easy and some are closer to ultra-hardcore difficulty level (and the order seems to be pretty random, or then some of the missions don't just fit me). There aren't many different enemies and practically no bossfight. The online is competetive co-op up to four players. It's playable and worth to consider, if you have the need to shoot something.

Orbient is kind of fun. Since your planet goes only forward, you control it with by pressing 1 or 2 for positive or negative gravity. The aim is to grow bigger and get moons for your planet and you can also orbit another planets. Great game for playing for high score and there are loads of levels.
The minus side is that you're not going forward, the play area is just the size of few screens and once you far enough, you notice just goin around the area and come back from another side.

For multiplayer fun Art Style Rotohex seems quite interesting.

@Famousringo: River City Ransom is Street Gangs in Europe (great 2 player game though).

I didn't own it originally... and yes I am getting it (see the OP)