Dynasty Warriors 7: Empires retained the marriage/ love confession mechanics, and let you watch a short cinematic when they're triggered, in which the pursuing character either slips out a confession, or an oath of marriage, all very much sugar-coated, and some of the them may actually came to be quite a surprise given the character's established persona. It can be very unexpected to hear an arrogant Blood Knight like Lu Bu, or Dong Zhuo to heartfeltly proclaim, in their own rugged way, that you are the most important person in the world to them and they'll make sure that nothing will ever change that.
The Hypothetical Endings in 8. After all the extra crap you went through ensuring that many of your important officers avert their historical deaths, you're finally treated to seeing how the land has gotten better thanks to your efforts. And everyone in the Kingdom you chose gets to enjoy peace (doubly so if you choose Shu; it's basically Shu and Wu in an eternal, good alliance, and triply so for Wu, because Wu drags BOTH Shu and Wei into one big happy family). After the Bittersweet and Downer feel of the ending in 7, it's really nice to see that with effort, you can change fate and create a better future. With any Kingdom you want.
That last point hits home even more so in 8 if you get each kingdom's historical ending first (and you probably will). 7 had the mercy of ending at what could be called each kingdom's high point, even if history said it was all downhill from there. 8 plays out the entire story and doesn't pretend the kingdoms in question are anything but doomed. Working hard for that happy alternative is worth every minute.
The development between Liu Bei and Sun Shang Xiang as the series progresses, before it was given a brief mention and the two didn't interact at all but come Warriors Orochi and The Sixth game it expands on their relationship and marriage more with the two interacting and caring for each other with Her beside him at his death bed in 8 and in Shu's Hypothetical ending the two stand side by side each smiling at one another. In fact, both Liu Bei and Sun Quan put her happiness above their desire for conquest. Liu Bei spares Quan in 6 and Quan does so likewise in 7 so she doesn't have to shed any more tears.
A Meta example of this is with Wu's Hypothetical route. Even though Sun Jian and Sun Ce are still alive, they still willingly serve Sun Quan and acknowledge him as the Ruler of Wu. Considering how often Quan is overshadowed by his father and brother, (and while 7 started to rectify this) it's nice see Quan finally get some respect as the actual founder of Wu.
Guan Yu's reunion with his brothers in 7. After being chased out at Guan Du by Yuan Shao for seemingly being a traitor, Liu Bei has no one beside him except for Zhang Fei and Zhao Yun. Then Guan Yu appears before him, but a group of Cao Cao's soldiers are with him as well, and Zhang Fei thinks he has joined Cao Cao, only for Guan Yu to swat his would-be assassins away and walk forward, bows and kneels, having at last found them, stating that his place will always be beside them.
In 7, Dian Wei promises to help Xu Zhu plow his fields. However, Wan Castle happens and before he dies, he gives his life to save Cao Cao, regretting in the process he wasn't able to keep his promise (and in 7, this is basically unavoidable). But in 8, if you do things right and get the Hypothetical Route, what do you see in Wei's ending? The two working together as they plow fields, FOR REAL!
Also in the hypothetical ending, we see the resident Rich Bitch Zhenji approach Cai Wenji and approvingly nod before playing a song together... for Wang Yi. The two's music are enough to make Wang Yi finally smile for real instead of her usual brooding about 'how do I kill Ma Chao'. Though it kind of helps that Ma Chao is dead, it may also show that maybe thanks to Zhenji and Cai Wenji, Wang Yi wouldn't collapse after fulfilling her vengeance, she finally can find another purpose in life aside of revenge.
Cao Cao taking the remnant of the Yellow Turbans from Qing Province, men who are starving with no food and only fight so they could live to see another day, as his own troops and giving them fields and land to farm is another great heartwarming moment, as this shows his nicer side, contrasting the fact that he's often labeled the villain of the Series.
In 5, if you play as Pang Tong or Wei Yan in Mt. Dingjun. The latter will show his uneasy feeling because some of his allies in Shu are doubtful about his loyalty to Liu Bei. Pang Tong, however, comfort and encourage him and basically said he has faith on Wei Yan. This is a stark contrast to Zhuge Liang's faith in Wei Yan, which also allude Pang Tong and Zhuge Liang's rivalry/differences.