The open-source movement has shown that being able to showcase your contributions as a proof of your skill and/or dedication is a powerful motivation for participating. A similar incentive for Wikipedia would be a powerful force to draw new editors to the project and allow existing editors to spend more time on it without harming their career; unfortunately, due to the highly collaborative nature of Wikipedia, the value of one's participation is hard to measure for an outsider, which makes it very hard for contributors to take credit for value added to Wikipedia.
This is a hard problem that needs to be tackled gradually over time. A good first step would be the creation of a contribution summarizing tool which (unlike the existing ones that focus on statistics and are hard to interpret for someone not familiar with Wikipedia editing) highlights contributions in an easy-to-understand manner. To do that,
- come up with a set of achievements which are programmatically measurable and easy to interpret (e.g. user is the primary author of an article that has been featured, or has gotten a high number of views; has created N high-quality articles over some period of time; has started N important articles in a given topic; is in the top 1% of users by editcount)
- write a Toolforge tool for measuring them for a given user
- add a cache layer as the previous step will probably be expensive
- write a nice frontend for displaying them (probably some kind of contribution timeline; see e.g. Github contributor activity or Stackoverflow developer stories)
- write an API so that other tools can fetch and use the data
- maybe provide some sort of opt-in for making it public (OAuth, or freeride on the opt-in methods other edit counters use) to avoid people being negatively affected by how information is presented about them
- bonus: provide an UI for the user to customize the information presented about them (e.g. select which articles to showcase)
- the project homepage on enwiki
- the Outreachy 15 project where initial work on this task was done: T178688: Proposal: Develop 'User Contribution Summary Tool' (implementation plan).
- XTools and other edit counters