Unless you give technical reasons why you're not satisfied with the current solution, and unless you evaluate the financial side of the rewrite, all you will get here be opinions based on nothing but personal preferences. Which is, needless to say, something no business decision should be based on in general.
Edit: To elaborate a bit on the already said, generally the process of decision of a rewrite goes like this (in this order):
1. What's wrong with the current solution? Is there a list of real problems with it? Performance? Client asking for features different to implement, if at all possible?
Or are you just unsatisfied / bored with the current technology (this is an often case with technical staff who want to work with the new technologies).
2. What does the current solution "depend" on? Proprietary technologies? Are there alternatives to those in language B (in which you wish to rewrite it). Is it possible to do a rather direct rewrite of codebase or will a large part of it need to be differently structured (architecture wise).
3. Is the current staff familiar with language B? If not, is there enough available staff in the area where your company resides? Commercial support for language B - does it exists? (Do not rely on communities of volunteers for long term projects; they go from one technology to another as their interests change. For a let's say two decade application lifespan you need solid grounds in terms of commercial support.)
4. How many clients depend on the current solution? Your costs of their transfer (you'll have to provide technical support) to new solution? Costs of giving support for how many years to those that have not upgraded?
5. Financial analysis of the whole thing (this is best done by someone from the managerial level; take it as a fact that if there is one thing they value and know how to estimate it is costs.)
I deliberately avoided specifics here since you didn't gave many in your question. Also there is probably more which I forgot to mention ... but it's 2am in my part of the world and I'm starting to get ... zzz <-- sleepy