The jobs you are running under cron
should handle expected errors. It is unusual to have cron
jobs that periodically fail. Fix the programs so that they don't fail. That may mean you need to wrap them in retry logic that waits a short period of time, then retries once or twice. However, I don't really like the retry solution.
If you have jobs failing routinely because of a "network hiccup", address the network issues. If it is for other reasons, address that issue.
If you want to alert only if the cron job is no longer working (definition required), don't alert on the cron job failure. Build a monitoring process that can detect the problem. This can be difficult. If you are monitoring an update process, there can be a period where there are no updates that triggers a false positive on the monitor that assures updates are being done.
Make sure you have scheduled your cron jobs so that you don't have conflicting jobs running at the same time. A timeline chart may help.
You may be able to cobble together a monitor for your critical jobs that counts the failures and successes and alerts if there have been too many successive failures. This will require an extra step in the job to report its status.