Recommendations

This is the Chinese version of operation proposal. The only thing that is common is time traveling. Heart melting romance in both dramas are same

As our main plot is time traveling, both dramas are about this. It's different in many things. This is about a man who time travel to propose his first love and to stop her from getting married.

Same director Jeffrey Lau. Charismatic comedy and romantic at the same time in a Chinese folk story context. Cheese CGI but who cares! Beautiful natural landscapes and atmospheres. Good combination of chinese folk tunes with modern stuff.

Actor Stephen Chow now directs. Good casting, funny jokes and nice music and art direction in regards of character make up, costumes, and special effects.

Similar story but more with an erotic background, and how lust can drive you to unpleaseant places. It has a lot of humour and erotism, mixed with ghosts and demons, so it does not get very preachy about morality and lust.

Tragedy romance about love between two different spiritual realms, moral story, beautiful music and landscape atmosphere.

They remind a bit about each other plot wise and with the female leads. Both female lead have "good hearing".

Considering how similar the main couples are in these two dramas. I'm surprised it's not even recommended. The genre is completely different. Memory Lost is a detective drama. The elite detective team vs. a team of criminal masterminds.

But I think Memory Lost amends the main weakness of Love O2O. The lack of chemistry. Xiao Nai is more often creepy than charismatic. Bei Wei Wei rarely shows any emotion other than blushing. While handling of plot, side characters etc. is awesome. A romance drama is incomplete if you can't feel the chemistry between the leads.

On the other hand while Han Chen is pretty possessive like Xiao Nai it comes off as more lovey dovey rather than creepy. Acting of Bai Xin Ji is leagues better than acting of Bei Wei Wei. And you can feel the chemistry between leads almost immediately.

Comparing the two in Memory Lost you get a way better OTP and a more exiting plot, with good twists, in Love O2O you get excellent side characters and realistic geek environment (Unlike some infamous shows).

Both involve a female protagonist travelling back in time. They also become involved with important historical figures of that time and contribute in politics/strategies using their knowledge from the future.
Splash Splash LOVE is definitely a lot shorter, but it's worth a watch if you want something quick and succinct.

"I want to eat you" but I need you. Almost the same premise. it's just that now, it is Lee Seung Gi's turn to "crave" his one true love.

Games, Betrayal, Friendship,
Did you watch one of them and thinking if you should watch the other ? then I think you shouldn't waste time reading any more, JUST GO FOR THEM

The leads gain the chances through a third party to redo specific bits of their past. They receive the knowledge from that third party, and try to alter those specific bits of the past to end it on a happier note; at the same time altering the present they are currently in. The more of those bits they altered that built up, the more the future diverged from it's original course.

It also about food. The main story is quite different from hot and sweet drama but the common thing is that the romance revolves around food.

Boku no Ita Jikan and Sky of Love (Koizora) both show how one of the character's illness affects their relationship.

Both of the plots are based on a "contract marriage" where eventually both of the main characters start to develop romantic feelings for each other.