American Airlines offers the easiest upgrades on trans-Atlantic coach.
Even deep-discount coach fares can be upgraded for the cost of 25,000 miles and $350 co-pay. They have to be American Airlines miles, however, not credit card points. American Airlies also offers LFBU - load factor-based upgrades. These are $500 each-way, even if you bought a dirt cheap $300 ticket, but its a gamble because there is no guarantee it is offered until you check-in.
The only credit card points that are useful for upgrading to first class are American Express points. That's it, nothing else will be of any use. American Express points are 1:1 with Delta points. American Express points are also 1:1 with ANA (All Nippon Airlines of Japan). You can convert American Express points to ANA miles and get a busienss class ticket between the East Coast and Europe on select airlines that are partners of ANA. It costs 63,000 points.
Here is how to get the most value for the money using American Express points to upgrade. No other credit card company offers reasonably priced upgrade rewards.
http://boardingarea.com/blogs/onemi...f-american-express-membership-rewards-points/
Delta's SkyMiles program is absolutely horrendous for reward redemption, though.
American Airlines and United have the best reward programs, its actually possible to find seats.
If you get an American Express Platinum Card, you can purchase select business or first class seats and a companion travel for free, so its basically paying 50% for a business or first class ticket. The catch is that discount business class fares are not valid, but sometimes its not impossible to find a full-fare business class ticket for $4,000-$5,000.