Boxed Value Type comparisons

What i'm trying to achieve here is a straight value comparison of boxed primitive types.

((object)12).Equals((object)12); // Type match will result in a value comparison,
((object)12).Equals((object)12d); // but a type mismatch will not. (false)
object.Equals((object)12,(object)12d); // Same here. (false)

I understand the 'why'. I just don't see a 'how'.

The types are unknown until runtime, where they could be any primitive type from a datasource. That includes strings, datetimes, bools, etc. I've gone down the ugly route of writing an extension method that works out both types, and then casts before doing a '==' comparison: (For completeness, i included every primitive type, plus those i was interested in)

public static bool ValueEquals(this object thisObj, object compare)
    {
        if (thisObj is int)
        {
            int obj = (int)thisObj;
            if (compare is int)
                return (obj == (int)compare);
            if (compare is uint)
                return (obj == (uint)compare);
            if (compare is decimal)
                return (obj == (decimal)compare);
            if (compare is float)
                return (obj == (float)compare);
            <... and so on for each primitive type ...>
        }
        if (thisObj is uint)
        {
            uint obj = (uint)thisObj;
            if (compare is int)
                return (obj == (int)compare);
            if (compare is uint)
                return (obj == (uint)compare);
            <... Again for each primitive type ...>
        }
        if (thisObj is decimal)
        {
            decimal obj = (decimal)thisObj;
            if (compare is int)
                return (obj == (int)compare);
            <... Etc, etc ...>

The resulting method turned out to be 300+ lines long, which was fine (yet hideous), but now I need to do more than just '=='. I need >, <, <=, >=, !=.

Is there anything in Reflection that i could use for boxed value type comparisons?

Anything at all?