I like Meg Ryan. Her roles in When Harry Met Sally and Sleepless in Seattle are classics. But what the heck has happened to her lips??? Her lips do appear to have undergone quite a few changes over the years. She started au naturel (1st photo), then her lips seemed to enlarge and her mouth widen (2nd photo), and fairly recently (3rd and 4th photos) it appears that things are going back towards normal (or nearly that). Here is my take (totally unsubstantiated opinion here):
She appears to have had lip implants placed, most evident in her upper lip. Back in the late 90's many plastic surgeons used Gore Tex implants to "permanently" enlarge the lips. I put "permanently" in parentheses because most patients had them eventually taken out. The problem I see with Gore Tex implants (and most lip implants in general) is that they are too firm to look like normal lip tissue. This can cause the upper lip to look unnaturally stiff. In addition, it can also make the mouth look wider because the implant doesn't allow the lip to pucker normally. This result can be exaggerated with injectables like Restylane and Collagen, which surgeons use to enhance the borders of the lips. Her lips do appear better now, possibly a result of removal of some or all of the implant, or maybe just due to laying off the additional lip injections. I like her the best before she appears to have had anything done.
Unlike what you see on many celebrities, lip enhancement doesn't always look fake. I enjoy using Juvederm at this time to enhance lips, because it's a very soft, natural-looking substance which seems to stick around for upwards of 6 months, possibly more.