Expressions, idioms and popular turn of phrases are hard to translate because often there isn't an equivalent at all in other languages. I tried to think what I would say if I had seen an amazing film and what I came up with is just a lot of words, like : "c'est vraiment un super bon film ! Il faut vraiment que tu ailles le voir. Ça vaut la peine d'aller le voir au cinéma". So me insisting a lot = your "I can't say it enough". It's hard to talk without popular turn of phrase, but don't be a slave to your words. Try to rephrase your thoughts. Remember that there was a time in your life before your heard the first person saying "I can't recommend it enough" and try to focus on what you used to say back then.

Andrew, if you look carefully at what the two people who corrected your notebook entry wrote, you'll see that they both changed it to: Si tu peux regarder ce film, je ne peux que te le recommander. This means : '..I can only recommend it' 'ne -- que' means only. So this is not the opposite of what you wanted to say.

There is no preexisting expression to say that. But you can express with normal words. Je ne le recommanderais jamais assez. ( I would never recommend it enough)

Nothing quite as strong... Maybe "Je le recommande chaleureusement"! :)