While a simple graph is great for accessing data of one item and custom graphs offer customisation options, none of the two allow to quickly create a comparison graph for multiple items with little effort and no maintenance.
To address this issue, since Zabbix 2.4 it is possible to create ad-hoc graphs for several items in a very quick way.
To create an ad-hoc graph, do the following:
Your graph is created instantly:
Note that to avoid displaying too many lines in the graph, only the average value for each item is displayed (min/max value lines are not displayed). Triggers and trigger information is not displayed in the graph.
In the created graph window you have the time period selector available and the possibility to switch from the "normal" line graph to a stacked one (and back).