You can check that you are using the following option according to the man page you should be unless you explicitly turn it off.
lazy_itable_init[= <0 to disable, 1 to enable>]
If enabled and the uninit_bg feature is enabled, the inode table will not be fully initialized by mke2fs. This speeds up filesystem initialization noticeably, but it requires the kernel to finish initializing the filesystem in the background when the filesystem is first mounted. If the option value is omitted, it defaults to 1 to enable lazy inode table initialization."
Never used this myself as although formatting ext3 is not instant it's nothing compared to a non quick format of ntfs.