“J’aime” alone, is stronger than “J’aime bien”.

For exemple, with a people : “Je l’aime” means you’re in love, “Je l’aime bien”, it’s a friend.

Correct me if i’m wrong, but i don’t think.

When referring to things, it’s just a matter of degree and j’aime bien is actually stronger than j’aime. Roughly:

• j’aime cette chanson = I like this song
• j’aime bien cette chanson = I really like this song
• j’adore cette chanson = I love this song

When referring to people instead, je t’aime is the strongest, and there is a difference in quality similar to the difference between love and like a person in English:

• je t’aime = I love you
• je t’aime bien = I like you
• je t’adore = I like you a lot

When talking about things, I think you can safely consider J’aime bien as the default for everyday conversations, J’aime being stronger and slightly more formal/solemn.

You can use J’aime for absolute truths or things you would consider inappropriate to only moderately like

J’aime mon pays / ma ville

J’aime la vie

J’aime les femmes / les hommes

J’aime la liberté

Or all-time favorites of yours

(slightly old-fashioned in spoken language though)

J’aime danser

J’aime me promener dans ce parc

J’aime ce film

J’aime bien can also be used as a way of confirming or contrasting statements

Tu n’aimes pas faire du vélo ? – Si, j’aime bien (I do like it)

J’aime bien le surf, mais pas la planche à voile.

About a person, J’aime clearly translates to “I love” and J’aime bien, “I like”.

Sorry for the ridiculously long “answer,” but this is a subject that has long perplexed me as an Anglophone and with much help from my French wife I think that I’ve finally hit upon a theory that makes some sense to me and I’d “love” to have your opinion!:

First, regardless of the context, “j’aime” is, as you and most others here suggest, always stronger than “j’aime bien,” but it’s not a simple concept (at least not for my native-English ears and mind) so I wouldn’t say that it’s “simply stronger.” Since love is already the strongest positive sentiment possible that one can feel and declare for someone/place/thing, neither its meaning nor the French verb used to declare and express it, “aimer,” can be strengthened by adding adverbs, even positive ones that strengthen most other French verbs. Oddly enough, the sentiment and the verb are not only incapable of being strengthened by such modifiers, but are actually weakened by them.

But why does this “reverse intensification” occur and how is it explained? (and here’s the “not simple” part): Since “Je (?’)aime,” the pure, unmodified, ‘straight-no-chaser’ version already declares the sentiment to the fullest extent possible, positive modifiers (bien, beaucoup) can only serve to beg comparisons with negative modifiers (un peu, pas beacoup) to establish and describe degrees of love below the absolute ceiling expressed by the pure, incomparable version.
It’s a word, kind of like the words “unique” and “parfait” (please try to forget “plus-que-parfait” for now), that doesn’t need and can’t take positive modification.
In fact, just like with attempts to positively intensify “aimer,” whenever anyone does try to intensify “unique” or “parfait” by adding “très” to them, for example, it raises not only serious grammar issues, but also serious suspicions that “[the speaker] dost protest[/exaggerate] too much,” thereby calling into question the very uniqueness and perfection of the thing that they are describing.

As mentioned above, the French verb used to declare this incomparable sentiment, “aimer” (all alone, without modification), is always on top across the full range of contexts. “Aimer bien”/”aimer beaucoup”/etc. always take away from the full-blown sentiment, whether addressed to a person, place, or thing. Of equal importance (and perhaps hardest for me to finally understand) is that “aimer” (all alone, without modification) always means “aimer” to French ears, regardless of context.

What does change with the context, however, is what “aimer” means to French ears in each particular context. Whereas English ears seem to require/search for different words (love/like) for different contexts where “aimer” is used, French ears and tongues don’t, for they are capable of relying solely on the context to understand and convey which kind of ‘love” is being expressed.

Therefore, in French one can “love” one’s dog (up to the fullest extent possible for loving dogs); “love” one’s sibling (up to the fullest extent possible for loving siblings); “love” one’s friends (up to the fullest extent possible for loving friends); “love” a place (up to the fullest extent possible for loving places); “love” one’s husband/wife/lover (up to the fullest extent possible for loving spouses and lovers); and one can even “love” one’s video game (up to the fullest extent possible for loving material things).

Native French speakers have the glorious freedom to express the full meaning of love in all of the above contexts without ever having a pedantic Anglophone parent or mentor reminding them that “You might ‘like very much’ your video game, but please don’t say that you ‘love’ it,” and without ever being accused childishly of “doing it” with their dog. This freedom is made possible by their audiences’ French ears, which are capable of knowing immediately what kind of “love” is meant depending solely on the context,

The key for me is trying to avoid feeling obligated to only use “aimer” when only “love” seems to be the best translation in English and likewise, to avoid feeling obligated to always use “aimer bien” whenever “like” seems to be the best translation in English. When in doubt, I usually prefer to overstate the sentiment with “aimer” than to understate it with “aimer bien,” based on the reasoning that, while incorrectly overstating it will occasionally cause temporary confusion, amazement, and even embarrassment among the audience, it avoids causing the permanent hurt and disappointment that could come from incorrectly understating it.

So, fear of sounding too formal or old-fashion aside, don’t ever be afraid to say that ‘vous aimez cette chanson,’ or ‘les fruits,’ or ‘poser des questions sur SE,’ without reservation or modification, because you will be understood by French audiences.
Don’t even be afraid to say “Je t’aime” to a near-total stranger during a passionate, one-night-only love-making session, because chances are very good that your French partner for the evening in this setting/context will understand immediately that you really mean “je ne t’aime pas du tout” or at worst/best “je ne te déteste pas” and respond accordingly with “Moi non plus!”

(actually my wife claims that much of the above could also apply to the verb “haïr”/to hate, but that’s even further beyond my comprehension than this subject is)

If “j’aime” (I love, it’s great) is too unconditional and “j’aime bien” (I like, it’s OK) is too deniable, there’s also “j’aime fort bien” (I like it a lot, it’s good).

I would have said it has something to do with strength, that j’aime is stronger than j’aime bien (which is true), but I thought about it a little and the answer is way simpler.

1. J’aime is almost never used alone orally (by “alone” I mean exclude j’aime beaucoup for example).
2. J’aime bien is pretty much never used formally.

It’s tricky because there is very little formal contexts to use the first person (je). I’m thinking of speeches but it also includes literature that doesn’t try to reproduce spoken language : poems, novels, …

Songs are in a middle ground, often using casual language but also integrating very literal phrases and formulations.

About the oral usage, if you like something a little or mildly you’d say j’aime bien, if you like it a lot j’adore. J’aime used alone is so weird it’s one of the main recurring jokes in the OSS 117 movies. Look for “j’aime me battre” or “j’aime me beurrer la biscotte“. Or if you’re fluent enough, watch the whole movie it’s really awesome.