Not only is wired ethernet faster in Mbps (100Mb vs. 54Mb), usually the wired ethernet concentrator is a switched technology. This means that each device has a full 100Mbps pipe available. Wireless 802.11g is a shared 54Mbps service, so the more devices using the wireless access point, the less bandwidth available for each device. Also, wireless is distance-dependent, meaning the farther away the PC is from the wireless access point, the slower the connection. Rarely will you get full 54Mbps throughput in the real world.
Ethernet can also be 10Mbps (shared or switched), though, so maybe that's where your comparison came from. Of course, ethernet also supports 1Gbps and 10Gbps, too.
However, as Joe indicated above, the bottleneck in your scenario will be the DSL connection anyway, so wired and wireless in that situation will probably yield similar response times -- assuming each PC is only accessing the Internet and there is no internal device to device traffic.
