Some thoughts on the summoner spells. TLDR: Flash is more versatile Flash is immediate power Ghost gives more power overtime Ghost can be used more often
Conclusion: Flash is still clearly better Riot probably wants to nerf flash but don't want to upset the community
Ghost is potentially better on certain champs, like Hecarim. Oh baby, Ghost pony.
Flash would be on my top priority list of things to be reworked in the game. I've talked about this many times in the EUW boards. Riot won't do anything with Flash tough because, if they did, the backlash from the community would be OUTRAGEOUSly terrible.
I would change flash from a Blink to a Dash in the first place and then maybe give it something else just to prevent a possible riot from the community (hehe).
I don't think every champion should have acess to a Blink. Those types of skills are thematic to certain champions (Kassadin, Ezreal, Katarina, ...). A Dash, maybe. I'm not saying they should remove a quick mobility summoner spell, but a Blink is just too much. A dash with increased combat strength for a short duration (like Graves's E) would be a good idea. Also, the abilty to jump over terrain should be considered because some walls shouldn't be allowed to "dash" through.
But the community doesn't agree with me on that, so I don't believe they'll ever change it.
I wouldn't mind some minor nerfs to flash, such as a heightened cooldown, but as it as stands, the spell is good, and other summoner spells should be elevated to its level, not the other way around.
ghost is by far better on any champion, if the enemy team doesn't have perma slows or a lot of slows like 
I think ghost is really useful for the hyper carry marksman like jinx, and tristana, vayne. Jinx always is reliant on her passive to catch up or getaway from an enemy. You sacrafice your heal for a potentially stronger chase. As it scales equally with your ability to kite champions. Maybe add in a frozen mallet and then mobile or not they aren't getting away easily
I don't think you can compare versatility here
