Nostalgia versus snobbery! Round one! Fight!
VC's a neat chance to get back to old games, but Nintendo has always been fickle and made weird choices about their releases. Sure, we get to play Mario Kary 64, but we also get Ice Climbers. Ice Climbers? Sure they were cute in Super Smash Bros Melee, but their original game isn't much fun. And how many people still own and play these games in their original format? Or on emulators?
Live Arcade is full of new tricks. A lot of the classics they release have been renewed for slightly better graphics and online support, such as Doom, Street Fighter II: Hyper Fighting, and Ultimate Mortal Kombat 3. The problem is that a lot of these classic releases just aren't very good, like Paperboy. Live Arcade's few original offerings are largely by independant studios. But how well do they work? Are the improvements worth ten dollars? The original titles are often fun, but shallow, and interest in them quickly wanes even over the duration of the trial.
So while Nintendo's VC is a great place to find the games that made Nintendo great, it's still a show of Nintendo's fear of getting too ahead of the tech curve from a lack of new content (which may not be a problem forever) to a refusal to add contemporary features fans would love to see. The Live Arcade appeals more to players who want to see classics updated with online play and bits patched together of the best versions of each game, making a new "mix" of each one, but the list of titles remains iffy, the classics often being so mostly in memory rather than in quality, and the fresh content (Lumines and Geometry Wars aside) is struggling to bridge the gap between affordable and lasting.