Artillery's ability to support infantry on attack is its main "selling point" improving the hit odds of a single friendly infantry. Just remember; this ability doesn't stack and each artillery only supports one infantry (unless you have a tech breakthrough which increases this).
Artillery is also capable on it's own, itself having 2 attack and 2 defense, making it a well rounded unit.
In some games, Artillery can be pulled by Mechanized Infantry, increasing it's movement to 2.
Just remember that Artillery costs an extra PU/IPC over Infantry, you should try having as much artillery as you have 2/3 of your infantry.