for absolute utility and flexibility of configuration it's hard to beat the Rubbermaid Fasttrack system. not gonna win you any interior design awards - probably better suited for a garage aesthetically - but super strong, super easy to move wheel hooks around, and can take other non-bike accessories like broom hooks (helmet holders, in my garage) etc. if you install two rails in parallel you can achieve maximum bike density by staggering the handlebars. you will have to drill several holes in the wall, however, so get a good studfinder.
forgive the chaotic state of the garage in this photo, but you can see I'm hanging a tandem, a heavy mountain bike, and a bunch of others.