RE2 Ada versus RE4 Ada:
In my own personal opinion, Ada was a far more complex and interesting character in RE2 than she was in RE4. She seemed a little colder, yes. She didn't flirt with Leon or make cute little comments or give him teddy bear key chains (wtf?). She was harsh and almost crude. She used him for all he was worth. But she was also far more human. She fell in love with Leon and let her emotions take over. She, for all intents and purposes, threw her life away to save him. It was a weak moment for her, but also a very strong moment. She revealed that yes, women can be cruel and cold hearted, but they can be vulnerable and emotional too. But most importantly, she showed us that being emotional is not a bad thing. She did save the day, after all.
Ada's harsh personality in RE2 didn't make it easy to like her. You had to look beyond the surface and make an actual attempt to understand her character. Yes, she did some pretty bad things. She used Leon through most of the game. She was probably using her "boyfriend" John who worked for Umbrella. But she tried to correct her mistakes in the end. Isn't that what matters? Sadly, few fans were able to like Ada.
Then RE4 comes along, and they announce that Ada will appear. I remember seeing countless rants from angry fans, infuriated that Ada was going to be in another game. The words "slut" and "bitch" popped up too many times to count. The other side of the fan base was simply uninterested. I found very few people who were actually pleased to hear the news. As a fan of Ada from the beginning, I was of course very happy.
But there was something different about Ada when she walked onto the scene in RE4. I noticed it almost immediately. Capcom made her likable. And not just likable to her fans or those who at least accepted her, but likable to the general masses. They designed her to appeal to anyone and everyone, even people who hated her before. They began this by making her more sexy. Yes, she was beautiful in RE2, but it wasn't the normal sort of beauty. She doesn't wear provocative clothes or have a gorgeous figure. It was more of a classy sort of beauty. But in RE4, she wears a stunning red dress with a high split. She has a perfect body with curves in all the right places. So right away, the male fans start to like her. Then they change her personality. She's no longer cold and harsh, but flirty and witty. Oh, and now she even has uber awesome martial arts techniques to boot! What possible reason could anyone not like her?
It literally seems as if Capcom was sitting around in a meeting and someone said they needed another female in RE4. Someone suggests Ada and another person replies "But fans hate Ada!". So they decide to turn her into a fan-pleaser character who could be liked and understood by anyone. As a fan of the original Ada, I'm just a little insulted by this. What's worse is that now Ada's popularity has sky-rocketed. Everyone likes Ada now, but it's for all the wrong reasons. She's super-pretty and super-tough and super-cool now. Honestly, I think all these new Ada fans are just shallow. A good portion of them didn't like Ada in RE2 or simply didn't care either way. And now that Ada is extremely easy to like, they all flock to her and deem her their favorite character. It's pathetic.
But if you're one of the few (and the proud!) RE2 Ada-lovers, then pat yourself on the back! You knew she was awesome all along, right? You didn't need a dolled up version of her to make you appreciate her. So yes, I think RE2 Ada is far superior to RE4 Ada by any standard. The original is still the best!