I don't think 1 day in Tokyo is long enough (perhaps not even 2!). I actually liked Tokyo more than Kyoto. In fact I would consider going back to Japan just to spend a week in Tokyo, there are so many things I didn't have time to see.
It's too easy to dismiss Tokyo as 'just another big city' - there are lots of interesting things but you have to get out and about to see them. Tokyo also has a comprehensive network of metro/trains that are easy to use, so you can make your own way around. Kyoto has only two (I think) metro lines, so you'll be more dependent on buses (I was never brave enough to try that) or taxis.
Someone recommended this to me but in the end I didn't have time - I was too busy doing my own things:
www.tokyofreeguide.org/
If you end up in just one place like the central business district (all glass plate windows and marble-fronted buildings) then you will think that's like any other city. So you need to spread yourself around a bit to get the nuance of different areas.
There's a brilliant walk from one of guidebooks (Time Out or Lonely Planet) from Nezu station to Nippori station, through a lovely quiet area with old buildings, mostly just one or two storeys high (very unusual in Tokyo).
Ginza is the upmarket shopping area: fine for shopping but I wouldn't want to stay there. I was surprised at the Uniqlo shop, as I thought it had less variety of stock than the one in Oxford Street. On the other hand the Muji flagship store was amazing, but probably meaningless if you're not familiar with Muji in the UK.
Shibuya was hell on earth - think Leicester Square on a Saturday night, multiplied by 100. It was the only time I couldn't find my bearings and had to use my compass to work out which direction I was going in! Teens would probably love it though. And it has a big branch of Loft, a stationery/home store.
Edo-Tokyo Museum: well worth a visit. And you go past the main sumo wrestling hall on the way to/from the station (Ryogoku), and there's a lot of sumo memorabilia in the station concourse.
Shopping in Tokyo is amazing, but you have to identify which stores you want to go to and map out where they are (although if you're just there for one day you probably won't have time for that). Daiso is fantastic (upmarket pound store) but I didn't find one in Tokyo, so make sure you find one elsewhere (there's one in Aeon mall in Kyoto, just south of the main train station).
I really want to go back to Tokyo now...