İzmir is certainly worth a two or three days stay and makes a good base for visiting Ephesus, the single lost visited tourist attraction in the whole of Turkey, and other nearby attractions close to the town of Selçuk.
In the city itself, it is a pleasant walk along the sea front lined with bars and restaurants and running for about 3 kms from the dock area to Konak and İzmir's famous clock tower. There are excellent shopping opportunities in the Alsancak area behind and running parallel to the Kordon
The bazaar (almost completely closed on Sundays) and beginning behind Konak Square, though a distinct second to İstanbul, is still large enough to cover several city districts, including Kemeraltı as the bazaar is often called. It is well worth seeking out the Kızlarağası Hanı, an Ottoman kervansaray with interesting vaulted shops..
The Archaeological Museum (closed Mondays), close to Konak, is also well worth a visit,. Also the Agora dating back to the early 2nd Century BC and reconstructed during the reign of the Roman emperor Marcus Aurelius, located at the top end of the bazaar. Follow the signs!
Rising above the Agora is Kadifekale (Velvet Castle) is also worth a short taxi ride for stunning views across İzmir’s bay and city.
There are no really good beaches close to the city centre but you may wish to consider Foça to the north or Çeşme to the west.
The advantage of Çeşme is the choice of several lovely beaches. Our favourite beach is Altınkum, known locally as Golden Beach, with pale sand and crystal-clear sea although I have to admit the water is appreciably cooler. Lovely when you’re in!
For warmer waters due to underwater thermal activity and sea a wonderful aquamarine colour, head for Ilıca. Also Dalyanköy, just 4kms from Çeşme, with a crescent beach of course sand, also has a picturesque harbour with waterside restaurants and THE place to eat fish and drink Rakı!
The small village of Alaçatı about 9 kms southeast of Çeşme has in recent years been transformed into a boutique town with pavement cafes and craft shops but still has the best and largest market in the area on Saturday. The sandy beach, 4kms south of the village is also home to an international wiond surfing and water sports centre.
All these towns and beaches are all easily accessible by Dolmuş, the regular and inexpensive shared mini bus service.
Çeşme itself still retains very much of a Turkish atmosphere with the Genoese Castle dominating the sea front. The new Marina offers designer shops and restaurant with prices to match but is well worth a visit if only to see the multi-million pound yachts! There are hotels, guest houses, shops to and restaurants to suit all tastes and pockets.
If you haven't already done so, I suggest you post a similar question on the Antalya forum and then be in a position to make a decision based on your preferences.
If you decide on İzmir and/or Çeşme , please let me know and I will be very happy to provide any more detailed information you may require,
Edited: 8:21 am, May 03, 2012